Alright... I found this on wetwebmedia:
(http://www.wetwebmedia.com/optgwthfaqs.htm)
QUOTE
"My babies in aquarium have a little grow, I give them a good food and I do
any work for them,
But I think They need to Hormone or Drug for further grow and fast grow,
Do you know any drug or hormone for them?
<actually the contrary is true. When fish are growing in an aquarium they give off natural hormones that inhibit the growth of each other (and themselves!). What your fishes really need to grow is more water changes to dilute the buildup of these hormones. Professional fish farmers do daily water changes to grow their fish the fastest. Artificial hormones are only used to stimulate reproduction... but generally they are not used for growth>
Please write name and address of site,
Thank you very much,
Nader
And the whole thing gives no mention of the type of fish, so I would assume that according to this site all fish have this trait. Still, I tend to like to get several opinions.