Backyard Aquaponics
A place to discuss aquaponics

I am thinking about doing 3 4X4 grow beds while useing one 330 gallon IBC to hold the fish. Is 330 gallons enough for 3 4X4 grow beds(Each grow bed is about 8 inches deep)? Also how many tilapia would be suitable for that size tank and filtration?

When you say 4x4 what is your unit of measurement? Imperial (inches, feet etc) or metric (cm, m etc)?

feet sorry.

3 @ 4'x4'x8" is perfect for a 330 gal IBC You could even add a 4th bed of that size and still be good to go. I use one 4'x8'x12" (240 Gallons GB Volume) bed per 275 gal IBC. What media are you planning on using in the GBs? Everyone loves pictures.

J.B.

Awsome!! So from my hydroponic experience i would say hydroton(Clay balls) but i see some people using gravel/small rocks. What do you suggest? Also how many fish would you recommend. I was planing on using tilapia because it is my first time and i have heard that they are pretty hardy and good for beginners.

I am also planning on doing this in a greenhouse because the plants i am growing(Moringa olifera) would benifit from the extra heat/humidity. Because i am going to be in a green house i though that i should bury the fish tank to keep the temps lower as well as facilitate the draining process. I will get get some pictures up soon, i just need to get something to take a pic of first. lol

If you are going with tilapia, there is no need to keep the fish tank cool. They grow faster the warmer the tank is. There are some great greenhouse threads that are worth reading through. JT's greenhouse thread is one of my favorites.

I like river rock... it's cheap and plentiful here, and not hard on the hands.

I can only speak personally on stocking density... everyone has their own opinion on the matter. I stock to 30 Bluegill in 1 IBC, half that for growing out catfish. Next year, when I do tilapia in the fully mature systems, I will venture to do 50 per IBC. But, that is only because my weekly water parameter testing is showing that everything is being used as fast as it is converted (at the current stock rates)... 0 ammonia, 0 Nitrite, and 0-5 Nitrate even with a dead fish in the drain for a week or so before I found it. Everyone's system is different. My best advice is to read where other's are succeeding with similarly sized systems.

When getting fish shipped or delivered to remote areas there are definitely economies of scale. I'd rather make one larger purchase than two or three smaller. I'm thinking it would be better to buy a quantity of fish based on the expected size of my system even if I only have a third of it in place now.

I am currently plumbing a single 300 gallon IBC fish tank with 2 IBCs chopped for grow beds and sumps. I bought 9 IBCs to start, so after my initial setup I will have 6 more already on hand for the next level of expansion. I expect to have tripled my original system size within 2-3 months incorporating lessons learned from the first system.

I'm looking at buying 100 catfish (4-6 inch) starting with the single tank and dividing them into separate tanks as they come online. Does anyone see a problem doing this?

The problem arises when you realize that even small fish put out a lot of ammonia. It becomes false economy when they all die off.

So i am new to this but basically you can have a high density of fish as long as you have enough plants to filter the water?

Not so much number of plants, but sq ft of media surface area for the bacteria to colonize. The bacteria are really the heavy lifters in a system... the fish and plants are really just beneficiaries. As you have a similarly sized system in the works, I would err on the side of conservatism... 30 fish + 25% for potential losses per IBC. you can scale up as the system matures and your log (like mine) shows it to be feasible. Do you plan on doing a fish-less cycle? I would recommend it.

J.B.

thank you that helps alot J.B. What kind of fish do you recomend? I was thinking tilapia. Also how many fish?

I was planning on doing a fishless cycle, my friend was telling me that their are packets of bacteria that you can use to inoculate your water with to speed up the process. is this true?

Most people don't bother with the bacteria starters. The bacteria will be there. Cleaning a friend's aquarium filter in your system is a free way to get a "jump start." Also ammonia prevents the bacteria that converts nitrites into nitrates from growing, and that is the slower growing stuff. It is going to take some time because of that anyways.

Yes, beware the false economy of buying too many fish because you figure some will die off as well. If you grossly over stock a new system there is a high probability that you will kill ALL the fish. Also keep in mind that 5 lb of tiny fish use up a lot more dissolved oxygen than a single 5 lb monster fish. Also the little guys usually like a higher protein feed which will also put more demand on the bio-filters. So if you must buy too many fish at the start, definitely make sure you have the system well cycled up using fishless cycling methods so that your bio-filter will be able to handle the load and make sure your schedule for system expansion will keep well ahead of the fish growth since that initial overstock of fingerlings can become a really gross overstock of fish as they grow and lack of water, space, aeration, filtration etc will be looming as your possible fish kill approaches if you don't get your expansion done in time.

It really doesn't take that many fish to run a system. This is really problematic for people who only have fish farms with minimum orders of say 100 fingerlings around and all they have is an IBC grow bed to support 10-15 fish.

Easy number to start off with for those working in feet. Figure in a new system, a cubic foot of gravel media bed will support one fish that you plan to grow out to one pound. for the first season of a system, stock only one fish per cubic foot of gravel MAX. If you stock heavier than that you better have pre-cycled the system fishless first.
If you are growing channel catfish, don't stock as many since they get bigger than 1 lb in a season in a warm climate.
Most people aim for 1 lb with tilapia so I would say stock one of those per cubic foot of media bed.
Bluegill, after you are past your first season, you can probably stock up to 3 of them per cubic foot of media since most people will be harvesting them at about 1/3rd of a pound each. It may be possible to grow some of them out to 1lb but rare and would probably take more than one year. 6 oz is a perfectly respectable size for a bluegill. This is why when people eat bluegill, they usually have to clean a whole mess of them.

IMPORTANT NOTE. You can always use LESS fish.
I've had a system do just fine with a 700 gallon fish tank and 70 channel catfish and 1500+ gallons of gravel beds with additional extra add on plant growing methods like rafts, towers and NFT pipes and I probably could have done just fine with about half that number of fish (and actually much of the time it was a lesser number of fish because we start harvesting some of them at around 2 lb and will keep harvesting a few fish at a time for months.)