Kind of embarrassed to be asking this question since I am a fishery biologist. I just purchased a new house and it came with a rather large tank, 600 plus gallons, which is the reason I bought the house. This tank is a freshwater tank, and there is a particular fish in this tank that I can not ID. If I had a digatal camera or scanner I would show a picture. Anyway, the previous owner said it was a snake head, but I dont not believe it to be true. The fish I have does not have a swim bladder, resides on the bottom and hides in the many caves. The fish is long and slender, maybe 5-6inches. The head is round and a wide mouth. the jar bone does not extend past the eye. The pectoral fins are lobed same with the caudal fin. The dorsal fin runs almost the entire length of the body with a wide gap in the middle. The fish is a greenish blue, but the tail fin has orange color in-between the caudal bones. AT first the fish reminds me of large goby, but the fish is way to cigar shaped to be a goby. If anyone has an idea or guess as to what this might be, I would appreciate it. I have looked in every book I have own and do not see this fish.