I have 7 sea cucumbers (tiger tail species) in my 480 gallon reef tank. They do a great job cleaning the sand. While I always hear the stories of how they wipe out tanks I have yet to actually meet a person that had this happen to their tank. The only worries I ever have with sea cucumbers is power heads. If you have a power head they can be easily sucked into without a guard then there might be some risk. On occasion they climb the walls of the tank but if your sides are clean then you should not have to worry about them doing it often. I just found one of mine hiding in the magnet of a gyre pump and I was worried it might get sucked in but after night fall it had already moved on to a new location without an issue. I have only had once experience with a sea cucumber getting angry when I worked in an LFS and it looked like it shot out a tube of silicone into the tank as a defense mechanism when I was trying to remove it from a rock. I removed the sticky substance from the reef tank and nothing happened to that reef system as a result. I am sure there are some risks with these animals and they have poisoned a tank before but I think its a pretty rare occurrence.



