Backyard Aquaponics
A place to discuss aquaponics

Just a quick question for all the knowledgeable folk here...

My system is currently a run of the mill CHIFT PIST setup, with a 1000L IBC FT, 3 1/2 IBC GB's and a 1/2 IBC sump.
It's currently stocked with 100 very small silver perch fingerlings, and a few yabbies in the sump. I realise this is way too much to grow out but was hoping to offload some when they got too much to handle.

Anyway, like everyone seems to do, I'm in the process of expanding Plans are to add a similar amount of hardware as what I already have, in much the same setup; Another FT, another 3 GB's and another sump, so effectively doubling the capacity. As well as this, I'm adding a radial flow solids filter and a 100L K1 moving bed bio filter.

Water pump is 6500L/H, Media is 14mm Blue Metal, plus a 2000L/H Air Pump. I think that's all you'd need to know?

So, the question is, once all the new stuff is in place, how many fish do you think my system could handle? The plan is to stock some Trout over winter...

Thanks!

I'd run them as two seperate systems.... with the radial flow and moving bed filter... for the trout system...

And given the specs.... 50 trout would probably be plenty...

With 3 x GB's p[er FT and the solids filter as well as the biofilter I say stock up and see what doesn't work. Keep an eye on the water specs (pH, NH3/NH4 and NO3) and watch the plants for health. Empty the filters regularly and maybe set up an air stone in a bucket to mineralise the waste into fertiliser for your normal gardens...

With that much filtering going on and presuming you are keeping up with solids removal from the FT's, I think you cold get all those fish through to edible state.

You might want to watch your ST's for water quality as well - yabbies produce waste too...

Maybe look into getting some fresh water mussels for your sumps as well - or even in the FT's - apparently they are water cleansers par excellence.

The Silvers will go near dormant through winter... and the 3 x 1/2 grow beds would probably cope without a problem...

A "new" trout system however.... especially with an IBC fish tank.... wouldn't really cope with more than 50... feeding heavily... growing fast... waste producing trout.... (hence the recommendation to use the radial flow and moving bed)....

You could up the numbers to about 60... but it's not just the filtration... it's fitting 50-60 fast growing trout into a 1000L IBC... and keeping the aeration up to them...

Come the next summer... with increasing feed/growth in the Silvers (after trout harvest).... I'd suggest splitting the 100 Silvers between the two systems... (solving the current over stocking problem)

In my opinion, any more than 40-50 fish in an IBC FT is plain cruelty and bordering inhumanity.

+1 Charlie.

Also I seemed to notice a trend of stunted growth with lots of fish in one tank. You might get more mass in total, but smaller fish. Could just be my imagination though... Plus it is hard to compare fish from different systems. You get very different feed rates etc.

Eek! Perhaps I should offload a few now then? I thought, being so small, they'd be fine, at least for a while. Anyone need some Silver Perch?

I completely agree.... the small surface area of an IBC... sets up agressive feeding... some stock bully their way to the feed... growing faster/larger.... the others survive on the scraps....

The reason why (and I was being very generous in my numbers)... I wasn't recommending to a filtration level...

I added a few more trout... for precisely the reason that some would grow faster... and be eaten earlier than others...

But in general... you're both completely right.... anything more than 40-50 fish in an IBC.... is really just too many...

Nope... they're still small.... and wont grow to any where near plate size before next summer...

Just split them between the two tanks... when the trout come out...

Just out of curiousity... why did you decide to stock 100 fish in a 1000L IBC...

Yep, guess you followed some bad information that's out there, not your fault, but you probably want about half the number or less as others have suggested.... Lucky you came here and asked...

To be honest, I did know better. I've been lurking here for a while now. I guess I was just buffering against catastrophe while they were so small And I knew they grew slow, just not how slow. I did/do have all intentions of palming half off once they have some size about them. So in a few months time, if anyone is looking for some Silvers, drop me a line...

I'll jump in since this thread is active and ask about my possible stocking.
FT 360 gallons filled to ~320 (1200 L)
ST 2*96 gallons (700L)
GBs 350+/- gallons total (1325 L)
CHIFT/PIST, CF with approx 500 (1900L) gallons total water in fully cycled system
Currently have 3 comet goldfish (3-4 inches) and 5 sunfish (range from 3-6 inches)
Thinking of adding 5 channel catfish, and 20 or 25 bluegill, depending on availability.
Too many? Not enough?

thanks and sorry for the threadjack

No worries

I'm relatively new to this, but I'll take a shot at answering your question (Despite my grossly overstocked system ).

From what I can gather, you want to stock your tank by final/harvest fish weight ( the total weight of all your fish once grown out to harvest size), relative to the volume of your grow bed media. As a general rule of thumb, you should be stocking at a rate of 1kg per 100L of GB media.

So, you have ~1325L of GB, meaning your stocking density should be 13.25kg (~29lbs) (1325L/100L=13.25kg). This means if you were to harvest your fish at 500g (1.1lbs), you would want to stock 26.5 fish (13.25kg=13250g/500g=26.5kg of fish) This is regardless of what size they begin at, don't do what I did and overstock in case of disaster

If you really wanted to get into, it all depends on the surface area of your filter media (gravel/expanded clay, etc), dissolved oxygen, rate of water turnover, fish species, etc. And also if you decide to add any external methods of filtration such as solids removal and moving bed filters. But from my limited knowledge, this should get you started and what you propose sounds fine to me.

Hope I helped