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Why is one of my shovel noses growing rapidly and the other two are not?

I dont know but i have exactly the same thing, i have three lima shovels and one is around 14 inches and quite thick/broad while the other two havent grown past 10 inches and are fairly slim.

I have heard it suggested that the dominant fish of many species release a growth inhibiting hormone into the water to keep rivals within a group from growing as large, though i fail to see how this could be of any use in a large flowing body of water.

I also have the same, I have five shovels, all bought at the same time but relative to one another 2 are large, 2 are medium and 1 is really small. They all appear to eat anything, they out compete the 4 Syno Euruptus they are in with for food (and before I put them together I thought the synos were greedy).

Until I read this I was thinking about putting the smaller one into a separate tank to feed it up so it could catch up but maybe thats just how it is with these fish.

Maybe they are different species? In the last couple of years, there have been several new ones although I don't have the paper or know the differences.

Alternatively, have you checked to see if the smaller ones are males and the larger females?

Jools

Hi!!

What is the size of them and in what volume do you keep them??
In a group a fish there are always a dominant which will always grow quickly because of his position which allows him to eat more...
the other fish can grow slower because of the stress the dominant has put on them...with harassement and stuff...have to hide can't compete as much for food...

Cheers
Yann

I obtained them all at the same size, appx 3 inches. The big one is now about 7 inches and broad headed. The other two are appx 4 inches and slim.
They are in separate tanks and get exactly the same food.
I have noticed that the bigger one has a light brown colour on his top and the two smaller are a dark grey.

I have also read that the dominant fish releases a 'growth inhibitor'. If this is true, that inhibitor would not have quite the impact in a open system such as a tropical river or lake that it would have in a more closed system such as an aquarium.

naturalart

Quite a while ago (over 20 or 30 years) someone (from NL) did an experiment raising Brechydanio rerio. He kept a litter in a small tank (40 * 25 * 25 cm, 25 liters) and only 10 grew. Threse, however, grew just as well as the ones he put in a much larger tank (other litter).

At 2 cm he remouved the 10, and 10 niew dominant ones popped up,which grew much more quickly.

This way, he managed to get 4 times 10 fishes, which reached 4 cm almost the same date.

The other fishes had been small too long, and did not grow anymore.

His conclusion was that the small fishes which did not grow very fast from the start, were just as well as the fast ones. My conclusion would be that some grow inhibiting hormone does excist, that it is mainly active in small tanks, and that raising fishes we should be aware of this risk.

However, bac to Suribim, Grokefish had his in seperate tanks, so he does disqualify any growth inhibiting hormones theory for the outstanding question.

Jools wrote:Maybe they are different species? In the last couple of years, there have been several new ones although I don't have the paper or know the differences.

Alternatively, have you checked to see if the smaller ones are males and the larger females?

Jools

This is something i have thought about before, all three of my limas were bought some five or six years ago from different shops over a period of around 12 months, and although they look similar there are some differences in colour and shape. The largest is a thick wide fish of around 14 inches long and has a noticable green/yellow sheen to its head, the two smaller fish are much darker in colour and one of them is a very thin streamlined shape (but does not look in anyway malnourished) so it could be that i have at least two and maybe three Sorubim species.
Unfortunately with no litterature or pictures to work with there is no way of positivly identifying them to a species level.