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Small Tanks = Small Fish?


Puggle
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"They only grow to the size of the tank" I don't know how many times I've heard this lately - that if you keep a fish in a small tank, it will stay small no matter what its potential size is. I've never been game to try it. What happens? Do they stop growing (with no health problems)? Do they die prematurely, before they reach their full size? Do they become horribly deformed and die when their outside stops growing but their insides don't? I think they'd grow a bit slower because they're not in optimal conditions, then die prematurely. But I don't know for sure. Have there been any scientific studies on it?

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I've heard that loads of times too. I've also heard 'that fish will outgrow that tank in no time!' just as many times though. You may end up with stunted fish in a small aquarium due to less than desirable water conditions. Big fish make a lot of mess.. even when they are little and I would imagine a small aquarium could become toxic very rapidly. If the water conditions were maintained to optimum levels I would imagine the fish would grow normally. This is all supposition though since I've never tried it either.

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All my previous fry remained less than 4 cm long, not including fins. That was probably due to less-than-optimal conditions due to my neglection because they either had undesirable traits or because I got sick of huge spawns, especially VT spawns which were huge and full of undesireable traits. These were raised in 1L bottles.

I am very interested as to whether this will happen to me again in future spawns, as I plan on keeping numbers to a select quality few and will be able to devote more care for each one, and they will be housed in containers holding no less than 1.75L.

I do believe that bettas can be stunted in small containers with poor water quality, and that the poor water quality may play a role in causing defects too, i.e ammonia/nitrite can cause defects in growing fish because it suffocates the fish and starves it of oxygen etc. (according to my trusted lfs).

I am not sure about other fish though, because I have no experience with fish other than bettas. I know that goldfish can be stunted in small bowls but can become huge if given a large tank or pond.

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The tiny 43 year old goldfish in England proved that goldfish can be stunted by poor water quality. It was not only small, it was ugly and twisted and colourless:

http://news.bbc.co.uk/1/hi/uk/414114.stm

A fish that old should be well over a foot long.

Now if you take that and compare it to the goldfish in the Guiness book of records who were raised in optimum conditions and reached 48cm in just a few years of running water and over feeding... and you'd have a pretty good case for small bowls stunting growth.

I've heard arguments that it isn't all the hormones that do it tho... more water quality... so I expect that well-cared for fish will soon outgrow their bowls.

Edited by Bren MacFish
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Usually that statement is made for goldfish. Goldfish release hormones (or similar) into the water that regulate their growth, Thats why with goldfish, lots of waterchanges makes them grow faster. The opposite to that, with koi, they do no release any hormones into the water and will continue to grow no matter how big the tank is. Its really a matter of which fish you are refering to when asking about tank size and growth etc. :)

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I think koi release pheromones also. Certainly mine stopped growing when they got to under a foot, in the presence of larger koi. I think pheromones (usually from other fish, not the actual fish in question) and nitrates/water quality both play a role. I have never heard of an oscar that grew so big it tuned around one day and smashed its tank, and I have observed that when tiny goldfish are placed in a large pond they grow like buggery, but if they have sepnt a few months in a tank and are then placed in the pond, the growth spurt doesn't happen. I think they therefore do maybe slow their rate of development to suit the body of water they are in, and it may be difficult or impossible to 'kick-start' the growth back up again once water conditions improve. I keep all my juvenile bettas in 1L bottles until they are sold and all grow to normal size. I'd like to blame it on a rigorous water change routine, but (don't tell anyone) I can't.

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I've had REALLY runty bettas suddenly grow to full size when moved out of a growout tank and into a smaller but less crowded tank. With goldfish I don't know. I've got 2 goldfish and 4 black-banded rainbows in a 2 ft tank, and the goldies are still growing well. However, one of our offices has 6 or 7 goldies in a 2-footer, and they're all stunted. Several are not just small, but bug-eyed and hollow-bellied: obviously not healthy.

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But Lisa, don't your bottles have holes in them to go into the tank for shared water? Mine were just 1L bottles with the necks cut off, and did not share water.

no, mine are in separate water. None of the latest spawns share water once jarred. Avoids the pheromone issue.

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