In my opinion, I think the worst fish for a tank is a yellow brotula. They are a horrible fish for a show tank because you barely see them and they are very hard to feed and keep alive. They are no fun to have because you will most likely only see it with the lights off and a red light. If for some reason, you are looking to get this fish, keep it very limited with the live rock and shelter. Also keep the lighting dim for more chances to see this fish.