Backyard Aquaponics
A place to discuss aquaponics

I have been considering using tropical fish in my system, such as guppies, mollies, etc.
Because of their small size I am having a difficult time figuring out stocking densities. Assuming sufficient filtration, how many 2-3 inch fish could i have in 1200 gal?
Also, i dont think the tropical fish flakes are very nutritious, anyone have a suggestion for proper fish food and supplier in the US?

I get my food from a feed store (where they sell rabbit food, etc.). It comes in 50 lb bags.

Usually you stock based on the full grown weight of the fish (or if they're food, the intended harvest weight). So, decided how big they're supposed to get (weight), then use the fish weight to filtration ratio that floats around here (don't remember it off the top of my head). Search the forum for "fish filtration ratio" maybe.

So it's more of a fish to filtration ratio than a fish to tank size, unless you get ridiculous.

many "tractor supply" places sell fish food for folks with ponds..
+1 on feed mills

Sorry, I just saw you said "assuming sufficient filtration". I don't know.

just add 50 or 100 and the population will self level wherever it is comfortable

yer when stocking mollies or guppies gab a hand full and throw them in

I guess I should have elaborated a little more on the thoughts going through my head...lol.
What I have been thinking about and would like to do is import tropical fish, keep them for a few weeks and sell them to local pet shops. Kind of like a wholesale fish warehouse aquaponic system. So I am not going to be worried about growing them out or giving them time to breed and multiply.... I am just having a hard time figuring out a safe stocking density. Most suggested stocking are /Lbs of fish @growout size. But how do I calculate it for 1-3 inch fish that I do not intend to growout?

I think your breaking new ground in the use of aquaponics for this sort of endevour. so its essientially a quarantine system for imported fish with aquaponics as the filter?

is that even legal? do you not have to provide exact details of the filtration and mechanisms by which to "sterilise" the system should a disease be imported? I know in australia, the chances of such a system being used for that purpose would be very low, but then, we have very strick import and quarantine rules.

perhaps the best way to start working out densities is with something like guppies. chuck 50 adults in the tank (10-15 boys and the rest girls). in a month that will be 1000 or more fish in the tank. Then watch and see how the system behaves. In 12 months you will have a really good idea of whats going on, and can start your short term growout/quarantine business then.

i do alot of indoor aquariums and with small community fish like guppies and mollies, in a 1000g tank you could start with a 1000 if you wanted. the main reason is because these fish are live bearing fish and have short life span. So when you buy them they are already adult size and could or could not breed. Ive seen 100 give or tank in a 40 gallon set up. sense your going to be moving them in and out so fast esp if you are buy them at adult age you will need to do so, hell just pack em in there id run double filtration than needed, which is agreed upon for most house hold aquariums.

A common rough estimate for aquariums with proper filtration is 1" of full-grown fish per gallon. Guppies being about 2" max full-grown, you could have about 500 in a 1000 gallon tank. Mollies closer to 250-300.
Deeper tanks that have less surface area relative to volume, and hence less oxygenation taking place, would have lower stocking densities.