There is a huge
40 page Wishlist in the SereneScreen Aquarium forum which has been developing since February 2001. Let's post requests for fish, creatures, improved backgrounds and new features there.
Let's reserve this forum area for Macintosh-specific issues.
As for the Firefish Gobi (the long white fish with red and purple fins), Jim has said that fish with very bright colors and odd appearances like that may not be coming to the Aquarium. I was incredulous, but that's what he said. He thinks having them would reduce the apparent realism of the Aquarium even though these are real fish that exist in nature.