Gradding Fish

[mellow1]

Grading fish by hand is a tedious and time consuming task. Want to make a couple of grader boxes, using a large plastic container, and PVC for the grading bars. The same kind of thing which can be seen on RBH thread about his fish farm layout. I would like to make one for grading small fish, and for larger fish, grading out 6/K from 4-5/K. What do any of you recommend on this, and what are good spacing measurements for the grading bars?

[RedBullHorn]

Trust me dude. Do not use PVC as the grading bar !!! you must use strainless steel bars only ! As catfishes are strong and PVC are soft material, PVC pipes are bendable, if you use PVC you won't get a good grading of the fishes. The wholesalers' grading box cost at lease 10'000 THB to build and it is made of stainless steel.

Edited August 22, 2010 by RedBullHorn

[wagner54]

Take RBH advice on not using pvc like he says because of the flex in the pvc you definately wont get accurate grading. I work in the fish business in Alaska and evreyone here uses the stainless steel pipe graders. If you have enough fish to warrant a grader spend the 10,000 baht to have one made with stainless. If its built with good stainless material it should be the last one you ever need. Good luck

[mellow1]

Thank you for the advice RBH and W54. We are still finishing off our second system, and 10,000 will go a long way towards that. Down the road though, a stainless grader will be purchased. At the moment, just to ease the workload, as well as to speed up the process, I would like to make a couple of cheap ones. A plastic container and PVC pipe will cost me about 400 Baht. The market in town and a few BBQ stands we supply are not so particular as the big buyers.

Please advise me on the spacing of the bars for these Pla Duk. For sorting 7-6/K and for 4-5/K. Or should I grade smaller then 6-7/K initially?

[mellow1]

Rhodes University recommends 6mm, 10mm, and 16mm spacing, but didn't mention for what size fish.

[RedBullHorn]

6, 10 and 16mm !?!!...NO NO NO ! ... get a #5 and #8 fish ( you'll have to kill it first ) then you get a caliper and measure the cross section of its skull. The box have 3 tiers and only 2 bars racks, any fishes that don't passes through the 1st bars rack are size #2,3,4 fishes/kg, don't pass through the 2nd bars rack are size #5,6,7 fishes/kg. And the rest at the bottom tier are size #8,9 and 10 fishes/kg. This are the standard grader sizes of the wholesalers, you may want to modify to your desired size spacing for your market.

Vernier Caliper

Cheers.

Edited August 23, 2010 by RedBullHorn

[mellow1]

So what's the proper spacing/ So far all your advice has been spot on.

[RedBullHorn]

I've just told you.... get a #5 fish ( 200grams) and a #8 fish ( 125grams) as on the post above yours.

Or if you're grading #6 fish / #5 fish and #4 fish, you'll need to build 3 separate bars racks...Still, i've to say this, you won't get a good grading with PVC pipes as they are flexible and bendy.

[mellow1]

I've just told you.... get a #5 fish ( 200grams) and a #8 fish ( 125grams) as on the post above yours.

Or if you're grading #6 fish / #5 fish and #4 fish, you'll need to build 3 separate bars racks...Still, i've to say this, you won't get a good grading with PVC pipes as they are flexible and bendy.

For some reason, I didn't see that post. Maybe too many Leos. I agree that the PVC will bend some, but we will have to live with it, till the farm starts making more money. We are mainly interested in getting the big ones out, and sorting out the smaller ones into 2 groups, in order to have approximate same size fish growing out in the tanks.

We just did the measuring, and have the materials to start. Looks like it will cost me 200Baht per grader box.

Thanks again RBH, for sharing your expertise.

[RedBullHorn]

Finally ! My long awaited 4'' fingerlings are here ! 100'000 of them ! I'm back in business !

water level...Check !

inlet and outlet pipes...Check !

Pellet feed...Check !

Anti Bac...Check !

Vitamin C...Check !

Lighting and cables...Check !

Jesus (Rottweiler)...Check !

Edited August 25, 2010 by RedBullHorn

[canuckamuck]

If you fill your PVC with cement they will become more stiff.

[RedBullHorn]

i second that.

[mellow1]

If you fill your PVC with cement they will become more stiff.

Great idea, thanks.

[mellow1]

Finally ! My long awaited 4'' fingerlings are here ! 100'000 of them ! I'm back in business !

water level...Check !

inlet and outlet pipes...Check !

Pellet feed...Check !

Anti Bac...Check !

Vitamin C...Check !

Lighting and cables...Check !

Jesus (Rottweiler)...Check !

Glad for you RBH. Nice dog.