Green water in concrete tanks (Tilapia)

[canuckamuck]

I have four concrete tanks of about 8000 liters each. I have done a nice job of fine tuning filtration and getting a good system in place. The water is generally quite clear and well aerated. My problem is that my Tilapia/TabTim are growing too slowly. It takes about 9 months to get to 500 grams. They get as much food as they can eat.

I know that they grow faster in green water, but I am wondering if I can create a green water setup in tanks that are so well setup to have clean water.

Has anyone tried to do greenwater in a tank, and what would be the recipe per liter for the nutrients?

[ozzydom]

For starters, fish do not grow faster in "green water" , they grow more cheaply,

If your fish are taking 9 months to attain 500g and the water is well aerated,and you are feeding to satiation something else seems to be out of whack.

I would ,at a guess think you are feeding 15.5 % protein food,Pla Nin and Tab Tim need at least 25% protein in clear water growing.

Using 16-20-0 fertilizer,12.5 gram per cub met of water should start the process(100 gram per tank),tanks should have full sunlight .

I dont know what effect your filtration will have on the process.

[canuckamuck]

I feed 30 to 32% protein. This is why I am assuming the green water is the difference. My fish get no green at all

[ozzydom]

I feed 30 to 32% protein. This is why I am assuming the green water is the difference. My fish get no green at all

Neither do cage fish and they get to 1kg in 6 months on high protein food.

what is your stocking rate in the tanks?

[T_Dog]

Are they sex reverse fish or are they reproductive?

[canuckamuck]

I often have 30kg of fish in an 8000 liter tank, so 266 liters per 1Kg bio-mass. When they are smaller the density is less.

Stocking rate does not seem to make a difference so far. They do get fresh water piped in from a stream continually as well, so I think I could stock much higher.

These are single sex fish

[T_Dog]

We have both reproductive and sex-reverse fish in our pond and the growth rate of the SR is about 8X normal. You might just be experiencing normal growth rates of Tilapia.

[canuckamuck]

Well I will consider some different suppliers this time around.

But what about a recipe for green water? That's what I came here for.

[canuckamuck]

I should add that these fish start out here as 2cm fry, not fingerlings.

[ozzydom]

Well I will consider some different suppliers this time around.

But what about a recipe for green water? That's what I came here for.

I gave it to you in post #2

[Pacificperson]

How much fresh water do you exchange? You should be getting algae from the feed and waste build-up in the system, unless you are flushing it all out. In that case, adding nutrients to the water will not do any good.

[cdmtdm]

increase the stocking density...... get the highest protein feed u can and block out the sunlight ..... i use 80 % shade cloth for 1 metre deep tanks , alage is a nuisance ...what is your DO reading ? what are your water tests saying ? ammonia , nitrite and nitrates ? and by the way PH ? very important

[canuckamuck]

Well I will consider some different suppliers this time around.

But what about a recipe for green water? That's what I came here for.

I gave it to you in post #2

Yes you did, my bad.

[canuckamuck]

How much fresh water do you exchange? You should be getting algae from the feed and waste build-up in the system, unless you are flushing it all out. In that case, adding nutrients to the water will not do any good.

This is a good point, and do worry that I exchange too much water to make the nutrients worthwhile. However I can lower the amount coming in.

[ozzydom]

I often have 30kg of fish in an 8000 liter tank, so 266 liters per 1Kg bio-mass. When they are smaller the density is less.

Stocking rate does not seem to make a difference so far. They do get fresh water piped in from a stream continually as well, so I think I could stock much higher.

These are single sex fish

I have read many claims regarding the numbers of fish that can be raised in tank systems, but upon investigation most of the claims are made by people with vested interests in marketing in this area.

At 30kg per 8cmt tank collates to 8 x 500g fish per cub metre.

We , after much experimentation stock at 2-2.5 fish per sq metre,last year the t/w double ordered and ended up with 4.5 fish per c/metre in one pond and the growth rate in that pond was 1/2 that of the other ponds.

We farm to get our fish to 700 gram in 8 months in green water with minimal feeding.

Our ponds are aerated 24/7 from when the fry average 200gram.

Your OP states your concern with lack of growth,my guess would be stocking rate, but you claim that you could stock much higher,so all I can say is up to you.

Feeding high protein and only attaining 500g in 9 months would put your balance sheet in the red which can only get redder the longer you keep them.

[canuckamuck]

increase the stocking density...... get the highest protein feed u can and block out the sunlight ..... i use 80 % shade cloth for 1 metre deep tanks , alage is a nuisance ...what is your DO reading ? what are your water tests saying ? ammonia , nitrite and nitrates ? and by the way PH ? very important

You have confused me, but this is easy to do

I am trying to get algae, not eliminate it. Tilapia like to filter feed on green water, it's free food. I was thinking to remove the 50% shade cloth I have.

As far as readings, I have done any in quite a while, but my nitrites were safely at the bottom of the scale last time I looked. I haven't done PH, and I would love to have a DO kit, but haven't come across a reasonable one yet. I will grab a PH kit this week sometime and have a look.

[ozzydom]

increase the stocking density...... get the highest protein feed u can and block out the sunlight ..... i use 80 % shade cloth for 1 metre deep tanks , alage is a nuisance ...what is your DO reading ? what are your water tests saying ? ammonia , nitrite and nitrates ? and by the way PH ? very important

You lost me, increase stocking density to get faster growth,get rid of algae which is part of Pla Nins natural diet.Lordy I am obviously doing it all wrong.

[cdmtdm]

perhaps you are doing it all wrong ....,,, try this increase the stocking density to around 1 kilo per 10 litres of water , get some competition in the tank to grow faster , your fish are lazy imo ... as for introducing algae into a tank culture ..forget it !! give them good quality high protein feed .... and make sure they actually eat it , dont let it sit in the tank uneaten ...... u must test your water , in a tank culture its a daily routine , if u have a problem u will know how to respond by what the water is telling u...

[canuckamuck]

I often have 30kg of fish in an 8000 liter tank, so 266 liters per 1Kg bio-mass. When they are smaller the density is less.

Stocking rate does not seem to make a difference so far. They do get fresh water piped in from a stream continually as well, so I think I could stock much higher.

These are single sex fish

I have read many claims regarding the numbers of fish that can be raised in tank systems, but upon investigation most of the claims are made by people with vested interests in marketing in this area.

At 30kg per 8cmt tank collates to 8 x 500g fish per cub metre.

We , after much experimentation stock at 2-2.5 fish per sq metre,last year the t/w double ordered and ended up with 4.5 fish per c/metre in one pond and the growth rate in that pond was 1/2 that of the other ponds.

We farm to get our fish to 700 gram in 8 months in green water with minimal feeding.

Our ponds are aerated 24/7 from when the fry average 200gram.

Your OP states your concern with lack of growth,my guess would be stocking rate, but you claim that you could stock much higher,so all I can say is up to you.

Feeding high protein and only attaining 500g in 9 months would put your balance sheet in the red which can only get redder the longer you keep them.

I missed this post OD, I don't think your stocking rate will get me very far, it suggests 16 fish per tank. If your right then how do the cage fish folks do it? They stock much heavier than you or me. I think the reason you need to stock such low numbers is because Tilapia are river fish and ponds are not optimal. However, you seem to have a good system, whereas I am renting fish.

[canuckamuck]

perhaps you are doing it all wrong ....,,, try this increase the stocking density to around 1 kilo per 10 litres of water , get some competition in the tank to grow faster , your fish are lazy imo ... as for introducing algae into a tank culture ..forget it !! give them good quality high protein feed .... and make sure they actually eat it , dont let it sit in the tank uneaten ...... u must test your water , in a tank culture its a daily routine , if u have a problem u will know how to respond by what the water is telling u...

This is an interesting theory and I have seen super dense operations on you tube. Stocking rate here would be heavily dependent on DO. I have toyed with the idea of direct O2 injection

You and Dom have opposite approaches. Do you raise fish for sale?

[cdmtdm]

perhaps you are doing it all wrong ....,,, try this increase the stocking density to around 1 kilo per 10 litres of water , get some competition in the tank to grow faster , your fish are lazy imo ... as for introducing algae into a tank culture ..forget it !! give them good quality high protein feed .... and make sure they actually eat it , dont let it sit in the tank uneaten ...... u must test your water , in a tank culture its a daily routine , if u have a problem u will know how to respond by what the water is telling u...

This is an interesting theory and I have seen super dense operations on you tube. Stocking rate here would be heavily dependent on DO. I have toyed with the idea of direct O2 injection

You and Dom have opposite approaches. Do you raise fish for sale?

yes its a very diff approach to pond culture , yes i do raise for sale ... get a DO meter about 9000 baht , an API freshwater master test kit 1000 baht , digital temp gauge .... then you will have an idea of what the fish are swimming in ...

[ozzydom]

I often have 30kg of fish in an 8000 liter tank, so 266 liters per 1Kg bio-mass. When they are smaller the density is less.

Stocking rate does not seem to make a difference so far. They do get fresh water piped in from a stream continually as well, so I think I could stock much higher.

These are single sex fish

I have read many claims regarding the numbers of fish that can be raised in tank systems, but upon investigation most of the claims are made by people with vested interests in marketing in this area.

At 30kg per 8cmt tank collates to 8 x 500g fish per cub metre.

We , after much experimentation stock at 2-2.5 fish per sq metre,last year the t/w double ordered and ended up with 4.5 fish per c/metre in one pond and the growth rate in that pond was 1/2 that of the other ponds.

We farm to get our fish to 700 gram in 8 months in green water with minimal feeding.

Our ponds are aerated 24/7 from when the fry average 200gram.

Your OP states your concern with lack of growth,my guess would be stocking rate, but you claim that you could stock much higher,so all I can say is up to you.

Feeding high protein and only attaining 500g in 9 months would put your balance sheet in the red which can only get redder the longer you keep them.

I missed this post OD, I don't think your stocking rate will get me very far, it suggests 16 fish per tank. If your right then how do the cage fish folks do it? They stock much heavier than you or me. I think the reason you need to stock such low numbers is because Tilapia are river fish and ponds are not optimal. However, you seem to have a good system, whereas I am renting fish.

Horses for courses mate,we have a finite market so we have evolved our stocks and methods to suit that market over the years.

Cost of production and hence profit margin is our main concern.

River cages have the advantage of multiple natural water changes per hour and no capitol or ongoing costs for pumping.

The disadvantages are higher food costs per high protein pellets,multiple feeds per day to 2% of bio mass and higher labour costs via the need to regularly grade and move the fish.

You do have some control over water quality in ponds whereas in free flowing rivers,when things go bad, they go bad bigtimeand can end up with the massive fish kills that have happened over the last few years.

[T_Dog]

One thing that promotes green water is morning glory and those bushy floating plants. We see our fish feeding around them or on them often. Might be difficult to do with a concrete fish tank however. Canuk... If you pass through Mae Taeng, send me a PM and I can pack up a few of those bushy plants for you. We planted two we got from a fish farm and now have a pond full!

[Pacificperson]

My guess is that you are flushing all of your nitrates out of the system and there are no nutrients for the algae. Nitrites will build-up in a system with bio-filtration, but no denitrifying filter,

Take a 20L bucket, put it under your inflow and time how long it takes to fill. From this, you can calculate your exchange rate. An example: 20L in 10 minutes equals 120 L/hr or 2,880 L/day which is a 36%/day exchange rate with an 8 ton tank. At this sort of exchange rate or higher, you can stock heavily, but you will not deveop green water.

Your 50% shade cloth will allow the algae to grow. It is not too dark.

[canuckamuck]

I looked around the yard and couldn't find anything I could use for measuring. I'll go to town tomorrow and get some 2 liter water bottles or something like that.

I think it is possible that I am running all the nutrients through. I am sure I have a bout 200% of the volume going out the drain daily.

Thanks for everyone's help here, I will continue to experiment this season. I will get some fry in Mid March if there are some available. I think I will run one tank at high density to see if that makes a difference.