Backyard Aquaponics
A place to discuss aquaponics

Okay, so just re-read some stuff and think there was a miss understanding about upstateap's question.

I think upstate and I are talking about stocking rate for fish (which he points out in reply to Jens), but Jensileadi is talking about the topic of sump size? Yes, no.

In this case Jens is correct on the calculation of water in a grow bed and how this translates to calculating sump. While i believe i am correct on fish stocking to media ratio. Sorry for confusion.

But Jens, could you clarify the following comments
"I thought it was water 40% to 3kg of fish but I could be wrong, I can't believe it because I've been running on this idea for the last 3 years!"
So please give us some hard figures about how you calculate your stocking density....i think you'll probably find it comes out <= the ratio of 3kg of fish per 100lt of media

Relax everyone. Don't make it too complex for yourselves.

The 40% thing is figuring the water needed to flood a bed and help one calculate the sump tank volume or how much fluctuation there will be in the fish tank and what not. Don't let it get mixed into ratios for fish stocking.

DrLuke has it right, stocking, NO more than 3 kg of fish per 100 liters of media in a system provided there is enough water/aeration for those fish in the system. That is a high stocking level. New systems should stock less fish. BYAP usually recommends 25 fingerlings into a system with a 500 liter grow bed I think (please correct me if I'm wrong it's been a while?) Here in the US I usually say start off stocking one fingerling per cubic foot of gravel (this is easy in systems where people know the square footage of their 12 inch deep grow beds, simply stock one fish for each square foot of grow bed since each square foot equals a cubic foot of media.) These recommendations are of course for fish that will only grow out to about a pound or 500 grams. If you are going to grow channel catfish the way I grow channel catfish, then stock fewer fish and then harvest some small to make room for the rest to grow out.

hygicell
Question: PS newboy on this subject.

The water outlet I have read, is done via a siphon system in the growing bed. I have to assume that the outflow of water is governed by the height of the various tubing and the amount of holes/slits in the outer tubing, is this correct. If I am correct then a selection of different siphons would allow you to vary the outflow of water. If however you were to put pumps into the growing bed how would the outflow of water be controlled also when would it know when to empty.

As a newbie I am a little confused as to why you would not feed your fish, this seems to go against the principle of the whole point of the system, surly fish are the slaves of our system and should be fed.