Backyard Aquaponics
A place to discuss aquaponics

Hi all - I have a fairly new system in my greenhouse that I just finally finished. It has been cycling with a few bluegill and plants. I currently have capacity for roughly 65-70 plants. The system's all up capacity is roughly 800 gallons of water. 2 media beds, 2 DWC beds, and 20 ft of pipe for NFT.

My question is how many tilapia would a system that size sustain, and are there any reputable sites to order from? I'm located near pittsburgh pa, so something in the CONUS would be preferred obviously.

Thanks for the input!!


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Not enough information to answer your question at this point, you haven't mentioned the size of any of the beds, gallons of media, square footage of raft surface... 60 to 75 plants tells us something but the filtration isn't really done as much by the plants, it's mostly the bacteria converting the ammonia and nitrites to nitrate. It also helps to know the capacity of the actual fish tank.

I'll give you a couple links to some guidelines since you have that information and hopefully that will let you figure it out but ask questions if you need to

Here's one measure for Maximum fish stocking for media beds - http://www.backyardaquaponics.com/forum/viewtopic.php?f=12&t=6646

For the DWC this has the UVI information - http://www.uvi.edu/files/documents/Research_and_Public_Service/WRRI/UVIAquaponicSystem.pdf

You may be able to reduce the feed requirement if you are able to mineralize the solids more effectively than they did. Anyway the rafts can neutralize more than you actually need to feed the fish for the plants to grow but while fish are very tolerant of nitrates I think it's best not to have super high and constantly climbing nitrates.

I suggest starting out at lower stocking densities till you get the hang of it and even once you've reached that stage it much easier not to go with the maximum stocking level.

Understood, thanks for the response.

I currently have 2 ibc tanks tied together with a 2inch pipe for my fish tanks, so roughly 500 gallons of fish tank.

I have 2 ibc "tops" 12 inches deep filled with lava rock, and 2 ibc "tops" 12 inches deep being used for the dwc beds.

i currently have 9 bluegill in the tanks. I know I'm drastically under stocked, and I'm looking to order some tilapia. I was thinking of ordering 40 to start with, but I'm scared of needing more. Every site I've found only sells fingerlings or fry. I wont be able to blend small and large fish down the line if I end up needing more. I'm just looking for a good, safe place to start on an amount. I've read many formulas on fish per gallon, and fish per plant, etc. I'm looking for some insight.. Start with 40 fingerlings maybe?

Based on your filtration you should be able to grow a maximum of about 80 to 95 lbs of fish but don't start out there your biofilter won't be ready for it and there is a learning curve along with having to watch the system more closely. I'd start with about 50 fish and grow them out to one pound - 25 in each tank. I figure the media beds can handle about 32 lbs of fish based on the link I gave you and the rafts can handle about 63 lbs of fish based on the UVI information. If you grow out 50lbs of fish, early on you'd probably have to supplement to get enough plant nutrients.

Calculations for the media beds - About 200 gallons of media but it will only be about 80% dampened so roughly 160 gallons functioning as a biofilter. 160/5 = approx 32 lbs of fish Maximum. Tilapia are pretty durable and I know there are people growing more than this but play it safe.

Calculations for the rafts beds - I figured you have 2.4 square meters of raft surface between the two IBC DWC beds. That should mean that the raft beds together can process around 430 gms of feed per day (based on UVI info 180g/m2/day if I remember right). Lakeway Tilapia has a pretty good chart for Tilapia size and weight and the feeding amount (https://lakewaytilapia.com/Tilapia-Feeding-Guide.php). Based on their chart at 453gms (1 pound roughly) each fish can eat approximately 6.8gms of food. 430/6.807 = approx 63 lbs of fish is the maximum the rafts could process the waste from.

So really stretching it to the max (don't) you could grow 95 lbs of fish. I suggest half of this or ending weight of 50 lbs of fish.

UVI says you need 60 to 100 gms/m2 of raft/day for growing the plants so you would need between 144 g and 240 g per day depending on what you're growing ((2.4m2 x 60g) and (2.4m2 x 100g)) and that's just for the rafts. You'll easily get this as the fish get older but when they are young you'll need to supplement to get enough plant nutrients. You could probably sprinkle some Blood and Bone in the media grow beds periodically to supplement at first (Probably two or three months).

So assuming I've done the calculations right (and I'm not 100% certain) that should get you in the ball park.

Great, thanks! I ordered 40 just to play it safe. We'll see what happens..


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Report back and let me know how it's going

Bump

Update : the 40 fingerlings finally arrived. All happy and healthy. However, I was surprised to see how small they actually are. They're about the size of my thumbnail. I hope they grow quick. It's really hard to find them in the totes they're so small. I have a feeling my system isn't cycling anytime soon with that small fish load.


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Patience is a virtue
Crawl before you walk

>> I have a feeling my system isn't cycling anytime soon with that small fish load.


It will be fine. You dont want a big load and as the fish grow the system will cope with it.
If you haven't yet cycled you need to keep an eye on things - particularly ammonia.
But with fingerlings you should be fine - they get larger pretty quickly.

Just avoid over feeding while the system is settling.

damn - duplicate message post and no delete option ?? [anyway deleted text as same as above]

I'm good at being patient, I just hope I get something before the end of the prime growing season. [FACE WITH STUCK-OUT TONGUE AND WINKING EYE]


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Irs5, by most definitions a 'fingerling' is called a fingerling because it is roughly the size of one's finger. Yours sound as though they were much more in the range of 'fry' when you got them.

Terminology aside, I hope they perform well for you!

where did you order them from?