The fish in the first and second picture is the same - it's a Black Ghost Knife - they're pretty cool fish, but they get pretty large. I had an African Brown Knife (which is a close, but much smaller, relative of the BGK) in a 30-Gallon, but had to give him away as everyone here said Brown Knifes (with a max of 10-12 inches) should be kept in only a 55+ tank. Since the Black Ghost Knife gets a bit larger, I'd have to say the tank would need to be larger, but it might be best to get advice from someone who has one.