I<3fish;4364682; said:Kelberi can and do grow larger than 18"... I would say 22" should be an appropriate max size. Monos can grow longer than 24", azuls can get as long as 36", and tems are known to reach 40". Either way, I think a 300g should be the minimum size for even the smaller/slower growers.
I was stating the probable max sizes. Do you have any pictures of these fish reaching this size in the aquarium? (other than a massive tank like The House of Sam or a public aquarium)