Want To Use Supercharger For Aeration

[mellow1]

My wife has set up some fish tanks (cement), to raise some Tilapia. She now needs air going into the tanks. We have seen a Supercharger at a fish farm in the past. We know little about it, except it produces a lot of air, and are not suppose to be expansive. I read that they are used for supplying air to engine turbos.

Have you used one? How did you set it up? What did it cost? Are there different sizes? Appreciate any help on the subject

[Boksida]

I have seen pickups transporting fish driving around with blowers belt driven by a small petrol engine. The blowers look like the ones on GM (Detroit) Diesels from of the two stroke series, e.g. 53 or 71, with any number of cylinders. Nissan also used to have a two stroke diesel UD series that had a very similar blower. The output side looked like it simply had a flange bolted on with an outlet to a hose. I could not see any method for lubrication attached - maybe the speed is kept low enough by the pulley size selection that it is not critical. I would think they would have high volume with low pressure, possibly very suitable for fish tanks.

I guess you would look for them at Sieng Kong shops in the area you live.

[Gary A]

A friend of mine has a jacuzzi built in his swimming pool. He has some sort of air pump that turns the water into a froth. I was amazed to see the huge amount of air it pumps. One person can easily pick it up and carry it around. It's not very big. Maybe you can check with a swimming pool dealer.

[WatersEdge]

Root Blower is the generic name.

Performance Data at this link

http://www.blowtac.com.tw/rb1.htm

They work wonderful for aeration.

I am told that at a second hand auto part store,

they are B3-4,000 for a diesel auto engine.

I bought a 2 inch outlet model, new,

Korean manufacture,

corresponding approximately to the MRT-50 on this data table.

from a Dealer in Bangkok, for B15,000

and was told it would require 2.5 hp

If anyone is interested I will track down the source again.

The above site is not the brand I purchased,

but performance is comparable from all manufacturers.

As a general estimate a

2.5 hp Root Blower would inject

3 m3 Air into water

2 meter deep.

The large fish / shrimp farms use paddle wheel aerators,

with many pontoons connected throughout the length of the pond on one drive shaft

because they are the most efficient way to aerate.

Their most visible advantage is their low tech construction,

compared to the root blower intricate tri lobe helix

The root blowers also will work for small scale grain dryers,

as they heat the air compressed

and they have a considerable pressure capacity,

forcing hot air through a deep stack of grain.

Root blowers also are a decent vacuum.

So that you can split the function of a grain dryer,

pulling ambient air through the first grain column,

and pushing heated air through the second column.

Considering the huge moisture penalty on grain price,

a root blower serving multiple purposes on the same farm would earn its keep.

As a methane compressor, a root blower could pull low pressure natural gas off the digester,

pulling it up through an absorption bed of lime

storing it much more densely in a low pressure air tank

Since the compression cycle is steady, the danger of impact detonation is eliminated.

[ozzydom]

The one we have fitted at the farm is a rootes type but is actually the one used on buses to provide air through the air con system. They have a wet sump so lubrication is not a problem, we use a 2.5 hp single phase motor.

I piped ours through 2" pvc piping to 4 ponds and reduce to 1 1/2 " along poles across each pond .

Each pond has 6 x 5" bubbler stones on 1/2 droppers. Each of those ponds is about a Rai each and 6 big stones seems sufficient,

Getting output data was a dead-end so I started out at 1100 rpm and finally settled about 1700 .

There is a bit of fiddling ,making mounting frames and fitting everything, if I were to do it again I would buy a cyclone style blower which can be had from larger fish and aquarium suppliers, they come in a variety of sizes .

Fisheries at Udon Thani have a large one aerating multiple concrete ponds and it has been going for years without problems.

[mellow1]

The one we have fitted at the farm is a rootes type but is actually the one used on buses to provide air through the air con system. They have a wet sump so lubrication is not a problem, we use a 2.5 hp single phase motor.

I piped ours through 2" pvc piping to 4 ponds and reduce to 1 1/2 " along poles across each pond .

Each pond has 6 x 5" bubbler stones on 1/2 droppers. Each of those ponds is about a Rai each and 6 big stones seems sufficient,

Getting output data was a dead-end so I started out at 1100 rpm and finally settled about 1700 .

There is a bit of fiddling ,making mounting frames and fitting everything, if I were to do it again I would buy a cyclone style blower which can be had from larger fish and aquarium suppliers, they come in a variety of sizes .

Fisheries at Udon Thani have a large one aerating multiple concrete ponds and it has been going for years without problems.

Thanks for the reply. I was thinking that a supercharger might be the economical way to go. Of course it will need an electric motor and a back up generator, but right now its getting the most for the money. That's why I wanted more info on that. Also would like some insight on the set up. I imagine a distribution manifold would be required, in order to distribute the air more evenly. Any links or advise are appreciated.

Thank you all,for your input thus far.

[ozzydom]

The blower ,motor, fabrication etc was about 15k ,plus another 10k for the electric timing and overload cutouts,switches etc.

I only found out that the cyclone type with integral motor was available when buying a smaller model for our nursery hapa,s , initial enquiries indicated that a large cyclone blower would have worked out about the same cost without the hassles.

Ours and all the blower setups I have seen are plumbed just like you were plumbing for water,ie. a 2" main line and reduced branch lines for each pond ,each must have a valve / stopcock to control the amount of air to each application ,and of course a valve on the end of your main line to exhaust excess air, the end should be directed under water as exhausted to atmosphere ,they sound like a jumbo jet .

Some applications use pvc piping fitted to the bottom of the pond and just drilled with small holes every foot or so but the smaller bubbling caused by stones is more effective than large bubbles .

A manifold would not accomplish much as each line would still need to be adjustable per valving.

[mellow1]

The blower ,motor, fabrication etc was about 15k ,plus another 10k for the electric timing and overload cutouts,switches etc.

I only found out that the cyclone type with integral motor was available when buying a smaller model for our nursery hapa,s , initial enquiries indicated that a large cyclone blower would have worked out about the same cost without the hassles.

Ours and all the blower setups I have seen are plumbed just like you were plumbing for water,ie. a 2" main line and reduced branch lines for each pond ,each must have a valve / stopcock to control the amount of air to each application ,and of course a valve on the end of your main line to exhaust excess air, the end should be directed under water as exhausted to atmosphere ,they sound like a jumbo jet .

Some applications use pvc piping fitted to the bottom of the pond and just drilled with small holes every foot or so but the smaller bubbling caused by stones is more effective than large bubbles .

A manifold would not accomplish much as each line would still need to be adjustable per valving.

Thanks again ozzydom. I went in to check with to hardware supplier that I use here for various things, and he said he would check into the Cyclone blower for us. My wife has set up 51 tanks, each holding a cubic meter of water. It's a recirculating system for Tilapia. The plan is to raise the fish to 1/2 Kilo in these tanks. The water pumps have been installed, and the system is being fine tuned. She is also arranging media for the filters, and experimenting with spray bars for the Bio filters.

As far as the blowers go, are there any other brand names which you can recommend ( if Cyclone can't be had here), and what size blower would you recommend also.

[ozzydom]

mellow1 , I will try to get a pamphlet from the agent here when I go to town .

There are a couple of sizes of used bus blowers available at the wreckers ,I would go for the bigger one you can find, it will take about a 2.5 motor to spin it.

Get the plainest one available, with a standard crank end to facilitate pulley changes. One I used was a disaster as I bought it sight unseen and it turned out to have a multi splined crank end and an electronic clutch pulley which was nigh on impossible to change ratios.

I have read a little about raising Tilapia in tanks but have never given it a lot of thought.,Have you a cost analysis on this form of growing out, how many fingerlings would you carry to 500gram in each tank?

One of the main problems is the market price available ,which is pretty stable at 70 baht farm gate retail and 60 baht wholesale , With low (16% ) protein food at about 25-30 baht kilo and 25% at up to 40 baht kg an FCR of much over 2;1 it becomes very marginal.

The only data I have seen was from the USA ,where costs are entirely different to here , I imagine retail prices are much higher but with fingerlings advertised at $1 each against the 50 satang here they would need to be.

I even tried value adding by doing skinned boneless fillets,but with !kg fish being the optimum for filleting and only a 30% recovery it meant a break-even price of 250 baht per kg retail price. ( another bright idea down the gurgler)

[mellow1]

mellow1 , I will try to get a pamphlet from the agent here when I go to town .

There are a couple of sizes of used bus blowers available at the wreckers ,I would go for the bigger one you can find, it will take about a 2.5 motor to spin it.

Get the plainest one available, with a standard crank end to facilitate pulley changes. One I used was a disaster as I bought it sight unseen and it turned out to have a multi splined crank end and an electronic clutch pulley which was nigh on impossible to change ratios.

I have read a little about raising Tilapia in tanks but have never given it a lot of thought.,Have you a cost analysis on this form of growing out, how many fingerlings would you carry to 500gram in each tank?

One of the main problems is the market price available ,which is pretty stable at 70 baht farm gate retail and 60 baht wholesale , With low (16% ) protein food at about 25-30 baht kilo and 25% at up to 40 baht kg an FCR of much over 2;1 it becomes very marginal.

The only data I have seen was from the USA ,where costs are entirely different to here , I imagine retail prices are much higher but with fingerlings advertised at $1 each against the 50 satang here they would need to be.

I even tried value adding by doing skinned boneless fillets,but with !kg fish being the optimum for filleting and only a 30% recovery it meant a break-even price of 250 baht per kg retail price. ( another bright idea down the gurgler)

Thank you for your interest ozzydom, I appreciate any info you can pass along to us.

In each tank ( 1000 liters of water) there will be 100 fish grown out to 500grams. They will be grown out in larger tanks to about 700 grams, at which point she will start selling.

Here(Issan) Tilapia go for 80 to 85 Baht/Kilo. My wife plans to sell them herself at the local market.

The fish will be fed feed which contains 35% protein, she previously used 32%, and the grew well and tasted very good. Tasted much better then pond raised. The feed goes for 470 Baht/20 Kilo. The fish will be sold live to the customer.

With no middle men, she should be able to make a decent profit. Small family operation, with 1 employee, maybe 2 if it goes well.

We are also going to check out the government fish farm around here, to ask about their ideas for aeration.

[mellow1]

Went to the government fish farm yesterday afternoon, to see their aeration set up. The men in the office were real nice and interested in what we are doing. We had been there before, and they were equally friendly, they even ran water tests on our water that first time

Anyways, they showed us their aeration set up for their tanks, and hatchery. Here they used both devices, blower and supercharger. They said that the blower is the way to go, and that the supercharger break's down a lot, and gives them nothing but headaches. They also said the blower is much quieter. We checked out the piping system for the air, and then looked around at other things.

They had a filter system for the tanks and one for the hatcheries. The filter system was minimal, in my opinion, mostly due to very little filtering media. They did however have a nice aspect to it, in that it contained plants. The plants looked healthy from all the nutrient they were getting from the water, but they could of used a few more plants. The water was quite opaque in the large tanks.

All in all, it was a nice and informative tour, and like I said the people where friendly, helpful, and told us to come back anytime. We already made inquiries about blowers after ozzydom's responses to this thread, and it looks like the way to go. Thank you for your replies.

[Maizefarmer]

A note regards aeration of water - in containers, pools, dams: injecting air into the water (through airstones or whatever) is actually very ineffecient. We all have this impression that an airstone at the bottom of the fish pond/tank, with lots of bubbles pouring forth is doing a good job. The reality is that nearly all of the bubbles will rise to the surface of the pond/tank without any O/CO2 exchange having taken place at all.

O/CO2 exchange in a volume of water nearly all takes place on the surface - the point of lowest surface tension. The key to effective and efficient aeration of a pond/tank is surface agitation. A 1hp motor driving a paddle system on the surface of a volume of water will provide something like 10 to 20 x's more O/CO2 exchange than the same 1hp motor used to drive a compressor to introduce air [through an airstone] at the base of the pond/tank.

Of course a paddle system may not always be practical on the back of a Toyota pickup, but I have seen them used. Placing a section of plastic gutter pipe verticaly in the corner of the tank with the top of the pipe about 1/4" above the water level, and with the airstone located at the base of the gutter pipe so that as the air bubbles rise in the pipe they draw water with them (just as divers use air inducted suction tubes for cleaning out debris on sunken ships), increases the amount of water the bubles come into contact with at the surface and increases the gas exchange efficiency.

[mellow1]

A note regards aeration of water - in containers, pools, dams: injecting air into the water (through airstones or whatever) is actually very ineffecient. We all have this impression that an airstone at the bottom of the fish pond/tank, with lots of bubbles pouring forth is doing a good job. The reality is that nearly all of the bubbles will rise to the surface of the pond/tank without any O/CO2 exchange having taken place at all.

O/CO2 exchange in a volume of water nearly all takes place on the surface - the point of lowest surface tension. The key to effective and efficient aeration of a pond/tank is surface agitation. A 1hp motor driving a paddle system on the surface of a volume of water will provide something like 10 to 20 x's more O/CO2 exchange than the same 1hp motor used to drive a compressor to introduce air [through an airstone] at the base of the pond/tank.

Of course a paddle system may not always be practical on the back of a Toyota pickup, but I have seen them used. Placing a section of plastic gutter pipe verticaly in the corner of the tank with the top of the pipe about 1/4" above the water level, and with the airstone located at the base of the gutter pipe so that as the air bubbles rise in the pipe they draw water with them (just as divers use air inducted suction tubes for cleaning out debris on sunken ships), increases the amount of water the bubles come into contact with at the surface and increases the gas exchange efficiency.

Good idea about the pipe and air diffuser, and therefore creating an airlift type system. Will try it out after I figure out what size blower to get.

[aitch52]

Hi Mellow 1, Ozzydom, Maize Farmer and all,

we have just started a similar operation to Mellow, built one 4 x 3 meter cement and block pond for Pladook Oui catfish, a second one is now being built alongside it, water depth 500 cms. I am considering options for additional aeration myself and also biological filtration, plastic media to grow the bacteria on, and layers of foam and carbon maybe. We have just treated the fish with a mixture that our local fry raisers prepared for us, Trimedved mixed into 3kgs of pellets, as a few of the fingerlings were head floating. All seems well at the moment. We are carrying out partial water changes with well water every 3-4 days.

I wanted to start with 1000 fingerlings to age the pond and see what happens but needless to say my wife pressurised by the family experts snuck out and added 1000 more. They are about 4cms long @ 70 satang each, notice you guys seem to be getting them for 55 satang. 7 have snuffed it so far, a couple more were revived by my Fathers rub em in salt method, he kept a fantail goldfish alive for 18 years doing that every time it looked a bit down in the mouth, the other one lasted 12 years heheh.

Like Mellow we aim to keep it small and don't expect a huge profit, sell the fish live locally from a stall at the side of the road, as we have a couple of large ponds on the family plot I am also considering Ozzydoms floating nursery method of raisng fry, cheers cobber for the info.

If nothing else it gives a joint interest and keeps us busy and if it fails miserably, well, easily converted into pig pens or ducks maybe.

Good Luck and Healthy Pla keeping!

Chris Aitch

[aitch52]

Also thanks to waters edge for the root blower info

[ozzydom]

A note regards aeration of water - in containers, pools, dams: injecting air into the water (through airstones or whatever) is actually very ineffecient. We all have this impression that an airstone at the bottom of the fish pond/tank, with lots of bubbles pouring forth is doing a good job. The reality is that nearly all of the bubbles will rise to the surface of the pond/tank without any O/CO2 exchange having taken place at all.

O/CO2 exchange in a volume of water nearly all takes place on the surface - the point of lowest surface tension. The key to effective and efficient aeration of a pond/tank is surface agitation. A 1hp motor driving a paddle system on the surface of a volume of water will provide something like 10 to 20 x's more O/CO2 exchange than the same 1hp motor used to drive a compressor to introduce air [through an airstone] at the base of the pond/tank.

Of course a paddle system may not always be practical on the back of a Toyota pickup, but I have seen them used. Placing a section of plastic gutter pipe verticaly in the corner of the tank with the top of the pipe about 1/4" above the water level, and with the airstone located at the base of the gutter pipe so that as the air bubbles rise in the pipe they draw water with them (just as divers use air inducted suction tubes for cleaning out debris on sunken ships), increases the amount of water the bubles come into contact with at the surface and increases the gas exchange efficiency.

Theory and practice are not one and the same thing,bear in mind here that we are talking commercial applications and not glass aquariums.

The stones we use weigh over 1 kg apiece,we run 6 per pond over 4 x 1 rai ponds simultaniously, using a 2.5 hp blower through 2" pipes .

The bubbles do not just rise to the surface ,they erupt ,throwing a geyser of aerated water and bubbles a foot in the air ,the agitated area from each stone covers about 9 sq metres which creates wavelets as it spreads out over the pond .

Paddle aeraters are not practical on smaller earth ponds due to the erosion they can cause.

Venturii effect appliances can be either water pump operated with air being introduced into the stream via back angled induction pipes above water or air operated ,drawing water from below surface for a similar effect.

We have been there and tried both ,but on a 1 rai pond it requires a 3" 5 hp pump to do a job inferior to the effect of 6 large stones using about 1/2 horsepower .

The effect on fish is in an aerated pond is amazing. To economise we run our aerater on two x two hour sequences per night ,(12-2 am & 4-6 am ) the period from midnight is we find the period of lowest available oxygen.

1000 kg liveweight of Pla Nin in an UN-aerated pond are early morning lethargic and oftimes sucking air on the surface ,they will not take food until sunlight or wave action has built up oxygen levels , mortality often occurs during this period and so health and growth of your stock is compromised.

On the other hand , fish in an aerated pond are lively and take food freely at first light, I suppose you could say they are happier,if there is such a thing as a happy Pla Nin.

[aitch52]

Oops got me cms and mms mixed up, 50cms I should say

[Maizefarmer]

A note regards aeration of water - in containers, pools, dams: injecting air into the water (through airstones or whatever) is actually very ineffecient. We all have this impression that an airstone at the bottom of the fish pond/tank, with lots of bubbles pouring forth is doing a good job. The reality is that nearly all of the bubbles will rise to the surface of the pond/tank without any O/CO2 exchange having taken place at all.

O/CO2 exchange in a volume of water nearly all takes place on the surface - the point of lowest surface tension. The key to effective and efficient aeration of a pond/tank is surface agitation. A 1hp motor driving a paddle system on the surface of a volume of water will provide something like 10 to 20 x's more O/CO2 exchange than the same 1hp motor used to drive a compressor to introduce air [through an airstone] at the base of the pond/tank.

Of course a paddle system may not always be practical on the back of a Toyota pickup, but I have seen them used. Placing a section of plastic gutter pipe verticaly in the corner of the tank with the top of the pipe about 1/4" above the water level, and with the airstone located at the base of the gutter pipe so that as the air bubbles rise in the pipe they draw water with them (just as divers use air inducted suction tubes for cleaning out debris on sunken ships), increases the amount of water the bubles come into contact with at the surface and increases the gas exchange efficiency.

Theory and practice are not one and the same thing,bear in mind here that we are talking commercial applications and not glass aquariums.

The stones we use weigh over 1 kg apiece,we run 6 per pond over 4 x 1 rai ponds simultaniously, using a 2.5 hp blower through 2" pipes .

The bubbles do not just rise to the surface ,they erupt ,throwing a geyser of aerated water and bubbles a foot in the air ,the agitated area from each stone covers about 9 sq metres which creates wavelets as it spreads out over the pond .

Paddle aeraters are not practical on smaller earth ponds due to the erosion they can cause.

Venturii effect appliances can be either water pump operated with air being introduced into the stream via back angled induction pipes above water or air operated ,drawing water from below surface for a similar effect.

We have been there and tried both ,but on a 1 rai pond it requires a 3" 5 hp pump to do a job inferior to the effect of 6 large stones using about 1/2 horsepower .

The effect on fish is in an aerated pond is amazing. To economise we run our aerater on two x two hour sequences per night ,(12-2 am & 4-6 am ) the period from midnight is we find the period of lowest available oxygen.

1000 kg liveweight of Pla Nin in an UN-aerated pond are early morning lethargic and oftimes sucking air on the surface ,they will not take food until sunlight or wave action has built up oxygen levels , mortality often occurs during this period and so health and growth of your stock is compromised.

On the other hand , fish in an aerated pond are lively and take food freely at first light, I suppose you could say they are happier,if there is such a thing as a happy Pla Nin.

Not sure where the cut off points are for volume/energy used/efficiency, but a quick read through your notes would seem to backup what I said earlier - that it's all about surface agitation. That is where the gas exchange takes place - on the surface - the issue then is: Can you introduce more air into the water for a given energy consumption by pumping the air down to the bottom of the pond and letting it rise up to cause surface agitation, or can you introduce more air into the water by agitating the surface, whether it be with paddles, with a corkscrew, or whatever else oe decided to use.

Don't know - thats all about equipment design I guess. What airstones do do, is lift water (with the bubbles) from the deeper layers (where the fish are?) to the surface. So whatever paddle system, or corkscrew (or whatever else is used) needs to be able to achieve, is move the water sufficiently to cause deeper layer water to mix with upper layer water, else the water down below is going to stay low in oxygen.

Decomposing organic matter at the bottom of the pond also reduces oxygen content - so removing organic matter on a regular basis would help, but at what cost?

I'm just sharing ideas, I've never really looked into the subject in much detail.

[steve73]

A simple but effective aerator for a pond the size of the OP's is as follows.

Use a small submersible pump (approx 200-300 W - 700 bt Makro/Tesco/BigC, etc), route the discharge horizontally (or slightly downward sloping) near the surface, via a 1" to 1/2" reducer to give it some velocity, and then slip a 2 foot (60 cm if you prefer) loosely over the outlet such that inlet is partly above the water surface and the outlet is a couple of inches below the surface. The water velocity from the pump will induce more water and also air into the 2" pipe, and a frothy mixture will be jetted just under the surface. Good for aeration, and the large flow give an efficient circulation to improve natural breathing at the surface. You'll need to experiment a bit with how much of the inlet of the 2" pipe is aboe the surface to get the best results.

This arrangement work well for ponds upto 30-40 m3. It's the same principlay as a Jacuzzi uses, known as a "Jet Pump"

Edited December 12, 2009 by steve73

[Spoonman]

Anyone got any pics of a jimmy blower setup as a pond aerator, im a big fan of superchargers but i normally see them on V8 engines.

[mellow1]

A note regards aeration of water - in containers, pools, dams: injecting air into the water (through airstones or whatever) is actually very ineffecient. We all have this impression that an airstone at the bottom of the fish pond/tank, with lots of bubbles pouring forth is doing a good job. The reality is that nearly all of the bubbles will rise to the surface of the pond/tank without any O/CO2 exchange having taken place at all.

O/CO2 exchange in a volume of water nearly all takes place on the surface - the point of lowest surface tension. The key to effective and efficient aeration of a pond/tank is surface agitation. A 1hp motor driving a paddle system on the surface of a volume of water will provide something like 10 to 20 x's more O/CO2 exchange than the same 1hp motor used to drive a compressor to introduce air [through an airstone] at the base of the pond/tank.

Of course a paddle system may not always be practical on the back of a Toyota pickup, but I have seen them used. Placing a section of plastic gutter pipe verticaly in the corner of the tank with the top of the pipe about 1/4" above the water level, and with the airstone located at the base of the gutter pipe so that as the air bubbles rise in the pipe they draw water with them (just as divers use air inducted suction tubes for cleaning out debris on sunken ships), increases the amount of water the bubles come into contact with at the surface and increases the gas exchange efficiency.

Theory and practice are not one and the same thing,bear in mind here that we are talking commercial applications and not glass aquariums.

The stones we use weigh over 1 kg apiece,we run 6 per pond over 4 x 1 rai ponds simultaniously, using a 2.5 hp blower through 2" pipes .

The bubbles do not just rise to the surface ,they erupt ,throwing a geyser of aerated water and bubbles a foot in the air ,the agitated area from each stone covers about 9 sq metres which creates wavelets as it spreads out over the pond .

Paddle aeraters are not practical on smaller earth ponds due to the erosion they can cause.

Venturii effect appliances can be either water pump operated with air being introduced into the stream via back angled induction pipes above water or air operated ,drawing water from below surface for a similar effect.

We have been there and tried both ,but on a 1 rai pond it requires a 3" 5 hp pump to do a job inferior to the effect of 6 large stones using about 1/2 horsepower .

The effect on fish is in an aerated pond is amazing. To economise we run our aerater on two x two hour sequences per night ,(12-2 am & 4-6 am ) the period from midnight is we find the period of lowest available oxygen.

1000 kg liveweight of Pla Nin in an UN-aerated pond are early morning lethargic and oftimes sucking air on the surface ,they will not take food until sunlight or wave action has built up oxygen levels , mortality often occurs during this period and so health and growth of your stock is compromised.

On the other hand , fish in an aerated pond are lively and take food freely at first light, I suppose you could say they are happier,if there is such a thing as a happy Pla Nin.

Not sure where the cut off points are for volume/energy used/efficiency, but a quick read through your notes would seem to backup what I said earlier - that it's all about surface agitation. That is where the gas exchange takes place - on the surface - the issue then is: Can you introduce more air into the water for a given energy consumption by pumping the air down to the bottom of the pond and letting it rise up to cause surface agitation, or can you introduce more air into the water by agitating the surface, whether it be with paddles, with a corkscrew, or whatever else oe decided to use.

Don't know - thats all about equipment design I guess. What airstones do do, is lift water (with the bubbles) from the deeper layers (where the fish are?) to the surface. So whatever paddle system, or corkscrew (or whatever else is used) needs to be able to achieve, is move the water sufficiently to cause deeper layer water to mix with upper layer water, else the water down below is going to stay low in oxygen.

Decomposing organic matter at the bottom of the pond also reduces oxygen content - so removing organic matter on a regular basis would help, but at what cost?

I'm just sharing ideas, I've never really looked into the subject in much detail.

Decomposing organic matter is a problem. We added a second 2" stand pipe in each tank, which has a 1 1/2" pipe inserted into it. It has holes drilled in the bottom of it. When you lift the outer larger pipe, while holding in place the taller, inner smaller pipe with the holes in it, the sludge on the bottom gets sucked out of the system completely, without ever making it to the filters. For sure we wont get all of it, but it should lighten the load on the filters. Either way, you got do water changes, so replacing the muck with clean water is what we are trying to do. Water changes also occur when cleaning out filters.

Besides the blower injecting air into the system, there are also bio filters (trickle towers in this case) where the water also gets aerated. The water leaves these filters and enters a manifold(larger pipe), which has vertical taller open pipes where air also enters into the manifold. The agitation of the water inside this manifold. along with the air, should further aerate the system ( my idea, so time will tell). It is then distributed to the various tanks via 6 lines which, also have vertical open pipes to continue the aeration process. The blower has been purchased for the air stones, which will be in the tanks,and some filters. These are now the final stages of this system, besides organizing and adding media to various filters.

[Maizefarmer]

Air lifts are extremely effective organic matter/suspended protein removal mechanisms - add ozone and they are even better: at the top of the air lift you havea surrounding overflow cup - protein matter will accumulate in the overflow cup as a froth - very effective, but can be over effective because fish tanks need a biological load to support fish - changing water can and often does dmaage the bio-balance in a tank volume, and so does/can ozone in a water lift - in much the same way as ultra-violet light steralizes water.

Its a cas eof getting the balance right.

[ozzydom]

I am following the venture of mellow1 with interest although I must admit to a certain amount of scepticism .

Cost of production will I feel be the big problem.

Using bio-filters means that any phytoplankton etc which are the natural food of Pla Nin and the main source of their protein is continually removed ,so their food intake must be provided via proprietry foods (pellets).In absence of natural food you are probably looking at providing about 5% of the fishes body weight per day to attain reasonable growth .

Pla Nin growth pattern is sporadic, they usually grow like weeds to about 200 grams then slow right down , lower temperatures (as at this time of year ) also retards their activities and growth.

Pla Nin in pond or green water do not need expensive additives such as fish or meat meal in their pellets as the protein is derived from the natural food available in the pond water ,in conditions where the phytoplanktons are removed then the pellets need to be high protein (and high cost) and much more of it.

The high electricity requirement of the closed systems is a big burden to profitability.

Fish fry producers use these systems, but the difference is the continual cash flow available because of the short span from hatching to selling.instead of the many months of growing from fry to market size

Market prices are fairly static,so if the market price is for instance 70 baht kg for fish 500 gram and above and a required profit of 20% nett then the cost of rearing and growing on must not exceed 54 baht/kg.

Production costs inc food,labour,capitol expenditure,mortality ,electricity etc must be contained to that cost .

The only person I know who was growing fish via the intensive method went bust and he had his own feed mill.

I am not casting the kiss of death on the venture as I wish mellow every success and hope it pays off for them, I am merely stating the way I see it from my own experience.

[mellow1]

^ I know whom you are referring to ozzydom. I believe his user name on this forum was tilapia. His farm is not far from where we are, and we have visited it, a number of times. He was/is involved with investors ( not a small family farm), and the last time I visited him, his fish were diseased. A disease he imported, when he bought the fish, and put them into his system. I believe he also had other problems not related to an aquaculture system,and not any of my business, he was always nice to me. We are small compared to his set up, have no investors or loans to pay off on this. The filtration system is completely different, easily cleanable, without any manual lifting. It can be handled by one person. It was designed to operate this way by me. I did not of course invent any of it, it all comes from information I have been reading about for about a dozen years. We did however build it to meet our personal needs, which is easy maintenance of all the mechanical filters, as well as all aspects of the operation. A one person job. My wife will not be selling her fish to a middleman, she will sell them in the evening at the local market. Yes there is electricity to pay , as well as fish food. But no matter what kind of fish farming operation you have, you will be pumping water somewhere, and possibly aerating. You will most likely be giving supplemental feed at the very least, if not all the feed the fish require. If you have ponds they will need to be drained to harvest, limed, left unproductive for periods of time. These ponds may also need structural maintenance when empty. You will also need 10 to 15 rie of ponds to achieve what will be produced on about a rie here. Either way there will be operating cost. We built two small experimental systems prior to this. We learned quite a lot from this, as well as operating them. One will be kept running as a quarantine for incoming fingerlings, prior to being added to the system, a lesson to be learned at tilapia's expense. I wish I could say it has all been easy going, getting to the point where this system is almost ready to go, but it hasn't. We are lucky in a way that it took a long time to construct, and we paid our way as we went, it would be terrible if one went into debt, and then having to repay while trying to make a go of things. At this point I cannot tell you of any great success rates in any aspect, but I do believe that my wife can make herself a decent living out of it. That is the reason it's being done. I also have no doubt that there will be many things to learn in the future from this, and various aspects will naturally morph. A little luck wont hurt us neither.

[ozzydom]

mellow, yes that disease almost wiped the industry out for a period, they still have not isolated the actual virus.

Samples were sent to labs as far afield as Scotland,Usa,Phillipines etc but biopsies came up with a conglomeration of about 5 virus.

Tabtim were hardest hit as they are not as hardy as Pla Nin.

I got it here, it is a horrible disease ,with lesions like cancer ,live fish swimming around with half their head eaten away or stomach hanging out At its peak we were losing up to 100 kg a day. Worst

I stopped all sales and as you could not buy antibiotic treated pellets I sourced the antibiotics and treated them myself.

I mixed the medicine in water and hand sprayed the pellets one bag at a time then laid them out on sheets of corrugated iron to dry after which I sprayed them with vegetable oil and allowed that to dry,the oil was to stop the antibiotic dissappating into the water before the fish got it down its tummy.

They were given two series of medication, one of 10 days and another a week later for 15 days ,all they got was the medicated pellets ,it seemed to work as within 6 weeks we had no sign of the problem and touch wood it has not re-occurred

Food of course will be your big cost,and keeping the FCR at a manageable level will be a priority.

Not so hard for us as I topdress our ponds every week with 5kg of 46% superphosphate to maintain a decent bio-diversity and population of zoo plankton and micro-organisms.

As an example of the different methods of growing on, Our pond number 1 is stocked with 4500 Pla Nin now about 230gram average size. I am only feeding that pond 8 kg of 20% pellets and 8kg of rice ram per day in total and getting fairly good growth rate , the beauty of supplementary feeding is it helps achieve a low FCR.

When we overstock like that we start selling about half the ponds stock at about 350-400gram then likewise for the next pond, this allows the remaining fish to gain weight up to 550-700 gram faster ,it also gives us two periods of cash flow per cycle.

[mellow1]

^ Disease is of a great concern to us. Your idea of spraying the food with medication is excellent. Never thought of that, and I would imagine, it would be the only way of treating fish in a closed system like ours. Do you have a link for the types of medicines used for various diseases? I have very little information on this subject.

We were likewise thinking of selling juvenile fish as you are doing, in order to get incoming cash during the long grow out period. Is there a good demand for such stock?, and what do you sell them for per kilo? Do you get a greater demand for pla nin or tap tin? Do you raise both? I have been reading both your comments, as well as maizefarmer's for a couple of years now and I appreciate the info gleaned from both of you, as I imagine others do also. Thanks.

I will try and post some pictures of the system we are trying to finish over the holidays, while we are not busy. This hopefully will give some constructive input which we may be able to apply in the future. It may also help someone else, wanting to do something similar.