Do fish only grow according to the size of tank?

[sealife]

The gentleman at my local fish store told me if you put a fish that grows large, in a small tank, it won't grow large and it will stop growing. It will not harm the fish and it won't shorten its life.
He then pointed to a 4 year old red devil he kept in what seemed to be 20g tank. And he said it just grew to the space the tank allowed.
Any truth in this?
Thanks.

 

[Jmunroe]

He is an idiot. The fish does suffer. It's internals will continue to grow. Eventually causing lots of problems. Fish release a growth inhibiting hormone which is one reason large frequent water changes are done during grow out. Because his rd has lived 4 years doesn't mean it is healthy and going to live its entire life expectancy. How big is the rd? Maybe he did enough large water changes while it was growing in its 20 gallon to avoid stunting and it just suffers from lack of space. I'm sure the water is toxic though unless he is changing 100% or more of the water daily. Again... He is an idiot.

 

[bettaowner]

I agree. Tank size will not determine the size of a fish entirely.

 

[Goldfish loach boy]

What an idiot, it's internal organs will continue to grow, so it's like filling a balloon with water, the balloon stops expanding and you know what happens next

 

[Sillyfishies]

Actually all of the above is wrong (except one post). It's the water quality not the water quantity. The fish puts out growth stunting hormones. This builds up a lot quicker in small tanks. Hence why they stop growing. So if a fish is in a small tank and its getting multiple big water changes daily, the proper nutrition, and stays disease free, it will continue to grow until its big as the tank (it's in that small of a tank!)

 

[sealife]

Actually all of the above is wrong (except one post). It's the water quality not the water quantity. The fish puts out growth stunting hormones. This builds up a lot quicker in small tanks. Hence why they stop growing. So if a fish is in a small tank and its getting multiple big water changes daily, the proper nutrition, and stays disease free, it will continue to grow until its big as the tank (it's in that small of a tank!)

So does this mean they can stay small in small tanks? I have no idea what kind of water changezs he does. But he once told me the standard water change for a healthy tank is 10% every 2 weeks.

The Red Devil was about 17 to 20 cm big in the 20g tank.

 

[Jmunroe]

So does this mean they can stay small in small tanks? I have no idea what kind of water changezs he does. But he once told me the standard water change for a healthy tank is 10% every 2 weeks. The Red Devil was about 17 to 20 cm big in the 20g tank.

Is this for real? Please don't listen to anything this guy is telling you. 10% every 2 weeks isn't a good water change schedule for 99% of tanks. Only the occasional heavy planted under stocked tank is going to survive this way. 50% a week is healthy on an average setup. If you have heavy bio load fish, do more. It depends on how much bio load in the tank and how fast nitrates are building up.
I have one for you.. a guy once told me you can keep an inch of fish per gallon of water. So I keep my 10 inch fish in 10 gallon tanks now. With of course 10% water change every 2 weeks. But they won't grow any bigger because they know they are in 10 gallons so they can only grow 10 inches. Don't want them to out grow their tanks.

 

[Jmunroe]

And if the RD is that small and 4 years old, it certainly won't live to an old age. Surprised it's still alive.

 

[sealife]

Yes its for real...
The gentleman seemed passionate about fish and said he was a fish fanatic and cant stop thinking of fish all the time. I'm guessing that's why he opened a store. He breeds a lot and sells them in his shop.
Its a very small store. He's the only worker in there. But gets some good fish from time to time.
Doesn't have large range of equipment. Mainly aqua one brand stuff for small tanks.
And he doesn't sell custom glass tanks at all. Mainly just focuses on live fish.
I don't know how he makes a living. Not very busy....

 

[Jmunroe]

Or smart

 

[sealife]

I actually asked him if he is part of any online forums. Since he was a fish fanatic...
He said no. Everyone overdoes things online. Like tank sizes and stuff.

I feel like a 15 year old kid in school, telling this story...

 

[Jmunroe]

Lol. Some are just old school and set in their ways. Most of them don't realize how long some species of fish actually live if looked after properly.

 

[Sillyfishies]

Lol. Some are just old school and set in their ways. Most of them don't realize how long some species of fish actually live if looked after properly.

"My goldfish lived a whole 2 years and I only scrubbed the tank every 6 months" - my dad

 

[Hobgob]

If they did research though they would find test done to prove them wrong.

 

[melosu58]

We used to have a marine biologist here at the site years ago. He was a pretty good expert. I asked him the same question and this is what he answered.

http://www.aquariumadvice.com/forums/f45/yellow-tang-in-a-55g-52207.html

 

[johnny leftist]

The whole "grow to the size of the tank" myth is one of the biggest contributors of early health problems, poor life quality and death in the hands of ill informed fish owners