Don't bother with them. They are pretty much pointless in tanks unless you like the random components or items that they drop. They do not make your tank glow their for they do not give you any gold and do not glow. So pretty much they are just there as a "Hey. my tank looks full."
My suggestion if you want fish that make your tank glow that are cheap, stick to any of the fish sold in Phin Phang or any low gold fish or mini monsters in the marketplace. ^_^
Sorry if you already know this just thought it'd be interesting to post.
