Backyard Aquaponics
A place to discuss aquaponics

Seriously guys sometimes you just over analyze the crap out of this. The op has a buttload of filtration and ft space and really has very little to worry about with stocking.

Stick to somewhere between 25 and 100 fish and you'll be fine. The more fish you get, the more closely you need to watch your water tests.

He really doesn't need to know the exact formulae and take harvest size etc into consideration with his first system. Just give it a go, stock fairly light and then min max it later once you're more confident and know your system.

The OP has 9000L of fish tank water.... so if we were to use the above.... that would be a max of 25 x 9 = 225 fish...

I don't think 100 fish is going to cause a problem....

3.8 cu m grow bed makes for aprox 57kg biofiltration capacity depending on the SSA of the media used with 100 fish the big eaters should start getting over the 700gr range (a good eating size) before you go over, agree with Rupe I would call 100 a good number.

They'll begin eating them @450/500gm... and will have to harvest them before summer temps get too high... so I doubt they'd get past the 700gm mark...

Ah OK well in that case they could go a little higher but being a new system 100 still makes for a nice round number, 130-140 could be safely stocked at 500gr harvest weights

Yep.... that's what I thought....

So lets say you had no calculator, what are the signs that your system is ready to take on more fish. Can you look at the plant growth as an indicator? Are there any particular species that you can use as an indicator? Or are you better off doing water testing? Might be a worthwhile experiment. Hmmm.

Water testing is better then any calculator, formulas can only tell you what should be, water testing tells you what actually is If nitrites and ammonia are at near zero levels and nitrates are running a touch low you should be able to handle more fish. Just use formulas to double check common sense, if you still have 40kg of fish swimming around adding another 100 fingerlings might be a bad idea unless you plan on harvesting out all the adults at once.
The basic formulas (or guidelines really) are easy enough you don't need a calculator, max of 15kg of fish per 1,000L of water and a minimum of 1,000L of media per 1,000L of water, and turn over your fish tank volume once an hour. Anything outside those general guidelines things get a little more complex as I am still learning.

What there needs to be is a canary plant for each nutrient. E.g.brocolli shows up a boron deficiency when there is a hollow stem, blossom end rot for calcium. Once I get my system up and running I will do research on all the major macro and micro nutrients deficiencies and excesses and will post.

Pics from your iPhone,Charlie put me on to the app iresize,cost 69p I used it on my ipad,could work for the iPhone as well....

Good stuff I will download as soon as my wifi dongle gets fixed. Then I will bore everyone to tears with my pics.

Ta da! Growbeds and little helper in the foreground, FTs in the background.

Maybe the FTs weren't in the background. Here they are!

FTs are buried 500mm in the ground. Going to order scoria tomorrow and hopefully finish plumbing in the next couple of days. I have 6 baby koi just getting things primed until my trout arrive at the end of may. I am so shocked that we managed to pull this off, usually our ideas only ever get half done.

Don't get too cocky.... you're only half done...