Backyard Aquaponics
A place to discuss aquaponics

i use 1 lb of fish per 6 gallons of grow bed media, but different people use different guidelines.

1 fish per 20-25 of the lowest of either fish tank max capacity or growbed wet capacity is the guide i recommend to clients. Especially for the novice and a brand new system.

I've harvest 650g fish out of an IBC and many people have had serious problems (mass dead fish) from stocking such numbers.

BC without pure oxygen injection you can keep LOW DO tolerant fish such as tilapia or carp at densities of around 60-70kg/m3.

The place we are talking about is a trout hatchery. The only way to keep trout at densities above 40kg/m3 is with pure O2 injection or MASSIVE turn over rates (tens or hundreds of times per hour).

That would be the 1:1 ratio.

For the 2:1 ratio 1 fish per 40-50L of media filtration.

ahh thanks.
I have:
400 high IBC's x4 = 1600 wet media
120ltrs half barrels x4 = 480 wet media
TOTAL - 2000ltrs roughly
so 2000/40 = 50 fish?

Then I have:
800 ltrs fish tank
4 x 400 ltrs sumps = 1600ltrs
TOTAL = 2400 Ltrs of water

I currently have 70-80 fish
trout and perch

I think that the ratios you guys discuss here are helpful for people with experience or who are plugged into a supportive community like BYAP forum. But that's not the people who get their stocking rate from the website of the local hatchery. They are likely complete beginners. So the rate on such a site should be quite conservative in the customers' best interests.

2:1? Is this ft:gb? If so what is the reasoning behind this? How does the ft volume lower the filtration capacity?
Sounds fishy.

The rates and ratios we give here are conservative. I don't think you will find anyone with any real experience on this forum recommending stocking densities above 25kg/m3 even though it is possible. Basically once you know enough to know what you are doing you know enough to know what is possible versus advisable. Until then everyone would be best advised to keep their stocking densities at or below 25kg/m3 with appropriate filtration.

My major point is that the stocking density on the website is not conservative and doesn't have any mention of filtration. While the second statement goes on to say 1 fish per 20L is fine it leads with the 1 fish per 10L claim and as we have seen it is all too often that new people stock their tanks to the higher level rather than the lower.

Went to the hatchery today and I got my new lot of 200 fish.

I spoke to them about their website and it sounds like it might already be an issue. The guy who helped me out said he wouldn't put more than 20 in an IBC but he also said that he doesn't do AP and apparently the guy who does who is also the guy who maintains the website. He has appreently assured him that 100 fish in an IBC is fine if you know what you are doing.

But stuart, did you not say to them.... "you are a fish hatchery, you are experts, AP is not some magical system, if you think 20 fish is enough, then your staff who maintain the website should be listening to you?" etc.

It is not a business.

Well it is a business but its not run for profit.

Basically the Fish Acclimatisation Society members all volunteer their labour. If you go their on open days it is very apparent that their are an awful lot of chiefs and I have yet to see an indian.

ohhhh ok fair enough.
a bit like glenburn, i thought that was a proper place too, untill i spoke to the guy and realised he is just lucky.

Did you have 100 or even 50 fish in the bulky?

I have had trout to a similar size myself in a bulky. But even with 15 odd fish,there was a big size difference. Like I said, I agree with you 100%, 50 fish in a bulky is ridiculous. But if you did manage to keep them alive you won't get many, if any fish close to 500g.

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