Backyard Aquaponics
A place to discuss aquaponics

1 run about 700 fish 300 silvers in 2500 litre, 300 trout in 2500 litres, 100 cod in 3200 litres, a few cat fish and gold fish thrown in for good measurse all with plenty of air.. my sump is 2500 litres. 1 run about 16 bath tubs along with 4 black tubs

That's a wide range, interesting! But still so far the stocking levels (or tank volume to fish qty ratio) are about what I was estimating. Safe at 1:20, mizzie I'm keen to see how your 300 go in 2500L. I guess if you turning over your total tank volume frequently enough and have lots of o2 then all will be good?

Burnsey---100 in 5000L---1:50
faye-------100 in 3000L---1:30
C1---------150 in 3000----1:20
OBO--------50 in 1000L----1:20
mizzie44--300 in 2500L---1:8.3

Also;
Air running 24/7?
and the usual fish to GB ratio of 3kg to 100L or above!

Just goes to show that there is no hard and fast rules. It varies also on the maturity of the system and size of fish. We aim to play safe and advise accordingly. 1% of fish feed would make absolute sense for a brand new system. Way different when the system is converting ammonia to nutrients and masses of plant growth are bulging out of the system and taking up the nutrients at a greater rate. Increased fish feeding at this time would easily be handled by a mature system.

So, what do you think about this Monya?

We are running no air, FT pump runs 15min on 45min off and have enough flow to recirculate about half of the flow back into the FT to aid in aeration. Sump pump is float switch activated and dumps about 300 litres at a time back into the FT (we have koi in our sump so keep about 250mm of water in it at all times).

3000 litres of GB

Our stocking rate was purposely low as we need a stable system that is essentialy over filtered - don't want HSM at school.

This is where some people get a little mixed up . Because the stocking rate is normally expressed in fish numbers or weight to keep it simple , but the reality is it should be expressed in feed rate per day.
Put simply , you should never put more food in than your bio handling capacity.
Plants have little to do with it as they remove mainly nitrates which are not deadly to fish until they are in VERY large amounts.
It is amount of feed balanced to bio-filtration.
Well that's how i see it anyway:)

Per-xacerly Chappo!!
It would be very helpfull (read 'invalueable") to operators of all systems, regardless of bio-conversion effiency, to be able to quantify this ratio of Feed in to Nitrites out.
Is there someway to measure this base rate? Say, 100grams of 40/60 food type (Protein/Carbs or other) to "X" square meters of bacteria laden media per hour for example. Or some other quantifiable ratio.
Any ideas?

Cheers IanK.

Yes and no Ian... there are formulas to arrive at oxygen demand and bio-filtration requirements based on feed rates...

But it's just not feed rate that determines the bio-filtration requirement... but more particularly the whole waste quantity... uneaten feed and ammonia wastes... these are not equivalent to the amount of feed input per day... some of the feed input is obviously converted to flesh, energy etc...

IMO... the figures, as Chappo partially suggests... are/or should be expressed as biomass (weight) to bio-filtration capacity.... if you have enough bio-filtration capacity to match your potential maximum biomass (see the suggested ratios)... then you'll have enough bio-filtration to cope with your maximum feed rate regardless...

Turnover is also a factor... as others have also suggested should be expressed...

But that's what the suggested stocking rates and growbed ratios are expressed as ... for simplicity...

There are calculations for this ,, ammonia processing calcs for different media etc.
Also expected Ammonia outs from defferent feeds , but it really has tooo many variables.

An example is Kaldnes bio media ,, it is rated at something like 200 grammes of hi protein food per day. But that would vary on oxygen input / filter set-up etc.
I guess the only realistic way is to push your system see how much it can take. Keep adding fish ( food) until you have ammonia/nitrate readings. The bacteria will multiply to adapt but eventually you reach maximum concentration of bacteria housing within your system and therefore have reached maximum food input levels.Another important variable here is temperature ,
For planning porpouses I guess there is little better than the experience already gained by members here.They undoubtably have pushed their system , some have pushed till breaking point , I believe called HSM

I've got 50 in 1400L (1000L IBC, 500L sump) filtered by two bathtubs (240L each) filled with scoria. And I've got 100 in 3000L filtered with two 500L beds filled with hydroton.

I also wonder how much temperature variations change how much your system can process - if you get a cold snap all of a sudden does the processing slow? The bacteria don't like being frozen.

Bacteria happiest in 15C - 30C ,, that is why Canberra was chosen as the Capital city , although the freezing conditions do not seem overly effective in the Parliament house:)

I think I have the power to delete this whole trouty thread.

Just to clarify, all my Trout are housed in two IBC's, but these are circulated every hour with the sumps (8000 litre) water capacity. Each IBC gets its volume turned over slightly more than once per hour, in a 15 minute pumping cycle. This really stirs the IBC up, and keeps them amazingly clear.

Air is on continuously from 3 seperate air pumps.

Sorta doing it this way to see how many fish can live well in 1000 litres, when its being circulated with a much larger water volume.

I know that a standalone IBC can hold 50 full size Trout, when circulating its own water to growbeds, but I cant recall anyone circulating an IBC with a much larger tank....

Total water volume 4500 litres 50 rainbows in one ibc 40 rainbows and 10 brown in another 60 silver perch in another and all the water interconected

Well, just do it!
Just because QLDlanders can't really do TROUT!!! AND they can't lose a football series, go for it!!
Cheers IanK