They are peaceful towards other fish, they mostly just like to be alone. Provide plenty of hiding places. They like a current to swim into, so provide a pump with a large smooth rock by the outflow and they will be very happy. Otherwise they will swim into your filter, trust me. You will probably still have to rig something on the outflow of your filter to keep it out. I use mesh on mine. They do a decent job of eating algea, but are not the greatest when it comes to kepping things clean. Make sure you provide algae wafers, and/or veggies or else it will starve to death. Mine loves cucumber. They grow to about 6-7 inches, and like all plecos, are major waste factories. Mine also is VERY hyperactive. I think it has ADHD or something.