I was wondering about the Pleco. I have heard and read that the room they are given in an aquarium will limit their growth. Is this true most of the time? It would be a 75gallon tank. I know they can get to be 2 feet long, and the 75gallon would be too small for that. But would the 75g tank be small enough to limit his growth to a size that will be ok in the 75gallon tank?