Backyard Aquaponics
A place to discuss aquaponics

I know that there are lots of different theories out there from 1 fish for 2 ltrs of water to 1 to 4-6. If sufficient food and water quality levels are maintained what are some of the high density fish to water ratios some of you have had successes and failures with???


Thanks

MM

Stocking densities should only be related to filtration capacity. We say 20-25 500g fish per 500L GB is a maximum safe level.

If you want to know what not to do, a friend of mine had 100 trout and 50 SP in a 2000L FT with only 600L GB.

They lasted 4 months.

I personally was a victim of the 1 fish per 10L of water bull shit. Luckily I was advised of the reality on this forum before a major HSM.

You can manage high stock densities but you are living on the edge and the life quality of your fish is disgusting.

Hi missionaryman

To answer your question correctly, you would need to specify what your priorities are.

Are you only interested in growing maximum number of fish ie aquaculture

do you want both fish and vegetables. ie aquaponics.

Aquaponics is a compromise of aquaculture and hydroponics, and as such is not better at either.

A friend of mine has his whole backyard as a hydroponic setup and consistently beats my AP
system. If he has a pest infestation, he just sprays the hell out of them with organic sprays
that if I used would kill my fish. He has no snails/slugs in his system and when he needs
to replace his solution he doesn't throw it away but waters his trees, so no waste.
But he gets his fish from me.

In aquaculture fish densities are very high but that is their business, they produce fish in tonnage.
They have biofilter systems, off-gassing tanks, swirl filters, nitrification tanks, direct oxygen
injection and so on. They monitor every aspect of their business all the time, it is a different
mind set, it's not a hobby it's their job.

But, to answer you question," 1 fish for 2 ltrs of water to 1 to 4-6 litres of water" may be pushing it.

But 1 fish in 10 litres I think is highly do-able but you won't be using gravel growbeds as
your filter/nitrification system. You will be going more towards the aquaculture system.

cheers Lou

My goal is actually more veggies... More fish more nutrients for the veggies right???

But that's the thing.. you don't need lots of fish to grow lots of veges.... you certainly don't need to stock "high densities"... although doing so might increase the overall profitability....

But it could very well work against you as well... especially if you're relying on large amounts of fish to pad out your bottom line... and, for instance, you can't necessarily rely on the integrity of your power, or water supply... and potentially could lose a lot of fish...

Copious amounts of vegetables can be grown with low stocking densities... and lower stocking densities are much more manageable... which in itself, if local knowledge is limited... might ultimately be a deciding factor...

Just keep in mind that many fish grow better, faster and healthier at higher stocking densities. Thats why you see people loading up at 1.5lb/gal on certain species. IMO, it is highly species dependent and then you have to weigh the cost of pure oxygen, oxygen cone, DO monotoring equipment, etc etc etc. If your bottom line looks better at higher densities, it may be worth the risk. To say that high stocking densities give the fish poor quality of life just isnt true. In some species sure, in other more predatory species it could be the difference between living healthy through the grow out period vs getting eaten by other fish in the tank. Quality of life comes down to using the correct equipment for the job and good HAACP practices.

I am starting with two 1000ltr IBC tanks. Water is cycled already. I have about twenty Moz. tilapia and Nile that i got at a local dam. I'm using 35 gal plastic storage totes for grow bed as we have an endless supply of them. No plants yet but plenty of nitrates and nitrites. I need to hook up a back up power system for the airation due many power outs here in Botswana. Any suggestions as to how many fish to start with??? I am linking the gb's together so i can expand however big i want. I would like as much grow bed space as possible while still maintaining the water quality so that i don't have fish deaths.

plent of nitrites are not a good thing! (if there are fish in there anyways)

The nitrites are now stable 'cause i have plenty of grow media now but these native fish i got at the dam must be extremely hardy. At first the nitrite levels were way beyond the "danger" level but none died. In fact they are growing very fast with my home made bean sprout fish food.

I asked a similar question and got a similar answer to the above. This is another way of saying 2.5kg fish per 100L of filtration (ie; growbed.)
The maths; 25 x 0.5=12.5kg. 12.5/5= 2.5kg/100L
Thats not 2.5kg of fingerlings, but rather what you expect the fish to be at harvest time. If you took 12 500g fish out and let the other 12 to grow to 1kg average, it still is 2.5kg/100L if you had that 500L GB.. Fish tank size is secondary to how well you can pull out toxins (plant food) and I think it relates more to the size of your pump. When I was caught aquarium fish for a living, the facility guys wanted to turn over the volume of the FT at least once every hour through the filtration.
Other places in here some people say 3kg/100L. Close enough. I was going to do this, but after listening to, among others, Charlie, I halved my stocking rate as my system is very new and I hate to watch fish kark it unless it's for a good cause (read BBQ!)
I also agree that some fish will handle company better than others (Tilapia for instance) while most predators are adapted to be territorial and aggressive by nature as they grow up.
Good luck, I hope this is useful.