General Fish Question:

[reef4me2]

Hey! Not really new to the hobby, but I just have general question regarding fish biology (that I'm sure some of the experts on here can answer!) and this seemed like as good a place as any to post it!

I've always heard that fish have indeterminate growth, but never really believed it 'til I was watching a show on the National Geographic channel the other day that said that as well. Do fish really have indeterminant growth? Why then do well cared for fish that get to live their full lifespan seem to attain a maximun size (and all the books by reputable people always include maximum sizes for different species)? I have some cichlids (with about a 20 year expected lifespan) that I have had for about 8 years that have grown any larger than around five inches (which is considered a "maximum" for their species), not having increased in size for several years. Does the growth just slow so much once the fish reaches adulthood that it is not noticible?

Thanks to anyone who can clear up my confusion on this topic!

 

[Johnny U]

I've heard that said about reptiles but not fish.

A related subject is that I've heard that fish won't outgrow their environment (i.e. if you put a gold fish in a fish bowl it won't grow to be as large as it would in a full blown aquarium.)

Is this true? My 15 year old son and I were talking about this and he said something about if we put a landscaping picture on our tank it'd "trick" the fish into growing bigger because he wouldn't realize he was only in a tank.

I told him he was full of it. Please confirm this so I don't have to eat crow. :lol:

 

[reef4me2]

I've heard that about reptiles as well... Seems feasible for crocodilians and some of the large constrictor species, but still seems hard to believe for all of 'em! I mean, I've never seen a 2ft long Green Anole, or a 7ft Bearded Dragon! LOL! This indeterminate growth thing is very confusing to me...

The only truth that's in the "a fish only gets as big as the tank it's in" is that the bioload on the tank will just get to be too much, and the fish will die before it can outgrow the tank... Kinda sad, but many aquarium stores tell people that's true all the time! A goldfish in ideal conditions may live to be 30+ years old, but in a bowl it's unlikely they'll make it past a month or two...

Can't go by the 1" of fish per gallon rule either since fish of the same length can have different masses. In other words (relating this to FW which I know more about), a 30g tank may support 15 cardinal tetras, but it certainly wouldn't support two 15" oscars.