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I have a 1000 liter tank and only a 180 liter growbed how many fish i should have in the tank?
Living in tokyo gives you very limited space.
Maybe about 20 medium sized ones?

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Afraid I'm going to have to disagree with you there, TC. In my opinion going with that much tank water to such a small grow bed is either asking for trouble by supplying too dilute a nutrient to the plants (i.e. if you stick to 10 fish) or, if you stock all the way up for that amount of water, be far, far too little filtration for the fish. The best thing is to add more beds!


TCLynx said:
Well, ya can probably have more than 180 liters of water but I would agree that you don't really want/need the fish tank to be full. Perhaps a little less than half full would be appropriate for the 180 liter grow bed.
Sylvia Bernstein said:
I'm with TCLynx on this one. With 180 liter grow bed you should only be filling that fish tank up with approximately 180ish liters of water, and stock accordingly (i.e. about 10 fish) to get the right concentration of nutrients to your grow bed, and also get enough filtration for your fish.
Hi Sylvia. Was just wondering if we consider the tank full of water as additional bio-filtration enhancing the bed capacity. The tank may even help with converting Ammonia, rather than the bed alone, and possibly help with a small amount of solids as well.What do you think?

Sylvia Bernstein said:
Afraid I'm going to have to disagree with you there, TC. In my opinion going with that much tank water to such a small grow bed is either asking for trouble by supplying too dilute a nutrient to the plants (i.e. if you stick to 10 fish) or, if you stock all the way up for that amount of water, be far, far too little filtration for the fish. The best thing is to add more beds!


TCLynx said:
Well, ya can probably have more than 180 liters of water but I would agree that you don't really want/need the fish tank to be full. Perhaps a little less than half full would be appropriate for the 180 liter grow bed.
Sylvia Bernstein said:
I'm with TCLynx on this one. With 180 liter grow bed you should only be filling that fish tank up with approximately 180ish liters of water, and stock accordingly (i.e. about 10 fish) to get the right concentration of nutrients to your grow bed, and also get enough filtration for your fish.
I'll agree with Sylvia on the dangers of wanting to stock to the tank. However, not knowing exactly the shape of the tank, simply only putting in 180 liters into a 1000 liter tank and then taking 40% of that water to flood the bed might leave a very very shallow amount of water for the fish. So I would probably fill the tank to whatever volume gives about 18 inches of depth and then strongly urge the owner to only stock about 10 fish since the grow bed capacity is so low.

I don't agree with the dilution being a problem. It will take longer on initial cycle up with the proper amount of fish to reach critical ammonia levels to really get cycling started but if dilution in more water were a problem, then raft systems would not work at all and definitely wouldn't work on low density systems which are now being proven viable.

Rather than dilution, I do worry a bit about being able to filter a larger amount of water through such a small grow bed. There is a point one will reach with a large fish tank but small amount of beds where you just can't get enough water through the beds to keep water quality good. Now I like systems to be at least 1:1 and try to get my systems up to 2:1 grow beds to fish tank but I do know of situations where people have kept fish with less grow bed than fish tank and they did manage so long as it was not too much less and they only kept an appropriate amount of fish for the amount of grow bed.

Having way less grow bed than fish tank definitely increases the chances of grow bed clogging.

The walls of the fish tank and the water in it might provide a little bit of bio-filtration but definitely not enough to really change the amount of fish one would be able to keep in such a set up. Adding more grow beds would be the best option.
Good point about the 18" of depth, TC.

In order for a system to achieve the coveted stated of balance both the fish and the plants need to be happy. We know how to do that by following certain guidelines in a media based system such as this one (1:1 to 2:1 ratio of bed to tank volume, approximately 1 fish per 5 gallons or 20 liters). My fear is that will be hard to achieve with this system set-up, Alfred, unless you "force" the tank to be smaller than it is by using less water than it is capable of. But I'm happy to be wrong...

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