A Red-Tailed Black Shark is a stunning fish, with a velvety- black body, a bright red tail, and a lovely streamlined shape. If you are going to keep a Black Shark in your aquarium, and I highly recommend that you do, only get one, because they get very aggressive towards others of their species. When they are younger they are relatively harmless, but as they got older and bigger they can get very cantankerous.
You need to give your Black Shark plenty of hiding places to choose from, like a flowerpot on its side, or some rocks or bogwood it can hide behind, because Black Sharks do need their own space, and get very unhappy when they can’t find a place to call their own. I have a shipwreck in my aquarium (an old ship made by my husband from a kit), that had holes made in the side so the Shark can get in and out. Whenever I take the shipwreck out to clean it the Shark gets very upset and sulks for quite a while. How do I know? He is no longer a beautiful velvety-black, his body is now grey, and he swims around chasing any other fish who dare to get in his way.
Do be careful also as your shark gets older and you buy new tropical fish for your aquarium. I had a problem a few years ago, that whenever I bought new fish, by the morning they were all dead. It took me a while to work it out, but the Black Shark would wait until I wasn’t looking, and then he would chase the new fishes around the aquarium until they died from shock/exhaustion. I didn’t know fish were that clever, but this one certainly was! I ended up giving the Black Shark to a friend who had a much larger aquarium than mine, which had a big Angelfish that was the boss of his tank. The Black Shark lived happily there for a few more years, with the Angelfish keeping him in his place.
You may know the Red-Tailed Black Shark as Red-Tailed Labeo, which it probably a better name, because the fish is in no way related to true sharks, so it is rather misleading. The scientific name is Labeo Bicolor.