Comment from Gene C: These fish will grow to the size of the tank and if bought young are suitable for tanks of about 10 gallons in size. They are excellent for cleaning the tank as they suck up much of the dirt on the bottom of the tank. If you have ornaments in the aquarium you will find the fish will attach itself to them in all different hanging positions. Have at least one in every tank! And they are very peaceful toward other species. They generally sleep during the day or when the aquarium light is on. Thanks for the comment Gene! I agree that Plecos are excellent fish but they are very fast growers. They can reach up to 18 inches in size. If you want to get a Pleco and you have a smaller tank just be prepared to get them into a larger tank when the time comes. Also, although I've never experienced it, I've heard reports of Plecos becoming aggressive towards their tank mates. All the Plecos that I've kept have always been very peaceful.