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 Post subject: dumb founded
PostPosted: Oct 27th, '15, 10:29 
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someone please help me understand the fish tank to grow bed ratio in kindergarten terms. for some reason I cannot understand it. I just built a system without a lot of research . now that I am researching it seems I have done things wrong. I have a buried ibc tote ( maybe 200 gallons) fish tank, which drains into a 55 gallon radial flow filter then to a ibc tote sump tank which has duck weed in it with 150 gallons of water which gets pumped to the grow bed which is 4 foot by 8 foot by 16 inches deep that fills and drains back to the fish tank. currently I have 69 tilapia that are about 5 inches long in the fish tank.

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 Post subject: Re: dumb founded
PostPosted: Oct 27th, '15, 10:52 
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Forget the growbed-fish tank ratio.

Work it out for 1 fish (that you'll let grow to 500g), for every 25L of wet media. So work out how many litres of wet media there is in your system, divide it by 25L, and it'll tell you how many fish your system can support.

Give the IBC of Aquaponics at the top of the page a read. It'll have all the information you need.

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 Post subject: Re: dumb founded
PostPosted: Oct 27th, '15, 10:53 
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but dont let the fish tank to GB ratio get too far out of whack either......

5000l of FT to 100l of GB with 4 fish is not going to grow anything but fish.


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 Post subject: Re: dumb founded
PostPosted: Oct 28th, '15, 08:36 
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thanks for the "help" I have read the ibc three times now, i must be missing something. maybe 50 pages or so of literature of ibc then maybe over a 100 pages of other peoples systems (show casing). which is wonderful but really has nothing to do with helping out. no where does it explain how to get the figures for the calculations mentioned in their teachings. which I think would be really useful in helping a beginner . I have read a lot of post concerning the same Question but they almost immediately get hijacked and go completely off topic because of the PROS on here. Sorry for being a beginner I know we must really bore the more advance society of the aquaponics world

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 Post subject: Re: dumb founded
PostPosted: Oct 28th, '15, 09:46 
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Have a look at this part through the IBC of AP:
http://ibcofaquaponics.com/guide-to-aqu ... -stocking/

It goes through the fish stocking part of it.

At the top, go through the guide to Aquaponics. It'll have all the beginners information you want.

We see the same threads pop up a lot, so the topics can go a lot off topic at times, but sometimes they can have far more information than the beginner wants. Which is why we usually point people to IBC of AP.

It's also tricky to know what to search for at times, when everybody comes in asking the same question in a different way. So the fish stocking questions has probably been answered in "Ratio thread", "Help, I have 1 fish per 10L and they are all dying", "how many fish?", "How much media?" "My ammonia won't go down", "How do I cycle", and so on.

But we're usually happy to help if you've searched and can't find the information you want.

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 Post subject: Re: dumb founded
PostPosted: Oct 28th, '15, 10:10 
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what wasnt "helpful"???

you said: "someone please help me understand the fish tank to grow bed ratio in kindergarten terms."

colum said: "Work it out for 1 fish (that you'll let grow to 500g), for every 25L of wet media."


cant get any more simple, there are no other equations that got us to that simple equation...


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 Post subject: Re: dumb founded
PostPosted: Oct 28th, '15, 12:37 
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Colum is correct in saying that the Fish:Gravel ratio (wet gravel) is the primary ratio you should be concerned with once the system is built and cycled, so you don't exceed the systems maximum safe fish stocking capacity, but as Yavi stated, the Gravel:Water ratio is also important, and it should be taken into account in the design stage.

It has been found that Gravel:Water ratios anywhere between 0.6:1 (typical of most single IBC systems with 300mm deep GB) and 2:1 will work fine... but the most widely recommended and the one most people seem to aim for is about a 1:1 ratio.

I've found that in my single IBC system with it's 0.6:1 ratio there are times when I can't fill the GB to it's maximum capacity with plants, such as when a new batch of fingerlings go in and there isn't much nutrient being produced. I normally only run leafy greens during these times and only 2/3 fill the GB, until the nutrient concentration starts to pick up.

On the flipside I've seen a few systems running up around the 2:1 Gravel:Water ratio and stocked to their maximum safe fish stocking capacity, producing too much nutrient, leading to Nitrate readings off the API chart, which isn't good for either the fish or the plants, especially seedlings.

A Nitrate test gives a good indication of how many plants you should have in the system at any one time and what types. Anywhere from 0.0ppm to 40ppm is fine for most plants. At 80ppm lettuce and some other leafy greens develop a bitter taste. At 160ppm you can have a hard time establishing seedlings in the system and the fish can also begin taking on a muddy taste when cooked. Readings constantly above 40ppm and I recommend that customers either add more grow bed, or reduce fish numbers.

Another issue I have with the 2:1 Gravel:Water ratio is that if a system is stocked to it's maximum safe fish stocking capacity (according to the Fish:Gravel ratio) the fish are packed in the FT with very little water and therefore oxygen per fish, plus increased water turbidity and suspended solids can also be an issue, so if there is problem with aeration they will die much quicker.

I always recommend a Gravel:Water ratio somewhere between 0.6:1 and 1:1 to my customers, but in saying that you don't need to stock a 2:1 system to it's maximum safe fish stocking capacity.

So the long and short of it is that you need to find a ratio that works with your system design/layout and work with it, around it etc... but anywhere between 0.6:1 and 2:1 is usually fine.

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 Post subject: Re: dumb founded
PostPosted: Oct 29th, '15, 02:19 
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I think the problem he may be having is in translating liters. Since you are in the states here is another way of putting it.
Say you have one 4ft x 8ft bed by 1ft deep, that would be 32 cubic feet of media. Multiply 32cft by 28.3168 will get you 906 liters. Divided by 25 (liters per lb of fish) shows you can stock up to 36 fish. A simpler and slightly lower stocking density is 1lb of fish for every cubic foot of grow media. Using that ratio would give you 32 fish for this example. Someone feel free to correct me if I am wrong.

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 Post subject: Re: dumb founded
PostPosted: Oct 29th, '15, 09:24 
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guys sorry for venting I should not have done that. this place is really useful but could be better like everything in life (a learning experience) it just sucks when something so simple fights me. I just could not figure out the volumes of the tanks after yall pointed me in the general direction for ratios. don't know what I was doing but kept coming up with a lot more fish then what I already had in the tanks. guess I could have reworded the question, but I wasn't thinking clearly. with all that said I am looking forward to being a student in learning about this amazing thing we are all trying to do. could you tell me if I have this right now? 48"x96"x14"=64512 cubic inches which is 1057 liters /25 liters which equals 42 fish? and if I need roughly 25 liters for every fish then that means I need 1050 liters of fish tank which would give me a 1 to 1 ratio? Mr. damage how do you get a .6 to 1 ratio?

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 Post subject: Re: dumb founded
PostPosted: Oct 29th, '15, 11:13 
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300L of gravel to 500L of water... Which are the volumes most people end up with roughly when building a single IBC system with a 300mm gravel depth (it's actually about 330L total gravel volume and the FT volume can be pushed to about 550L).

Also, that 25L of gravel per fish ratio that Column quoted is for wet gravel volume, not total gravel volume, so don't include the 1½"-2" dry layer at the top of your grow bed. This is important if you're figuring out your maximum safe fish stocking capacity, but not so important for figuring out your gravel:water ratio, which as you're now aware, is much more flexible.

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