I disagree with the idea of taking a fish back before he gets too big. Sure a plec may grow too big for your current tank, but if you buy a baby one - you can enjoy him until he gets a bit big - they you can return him and trade him in for something (supplies, or a new smaller/different plec). Better in the long run - emotionally? What? You can't mix Practicality and emotion and expect that you'll always come to the same conclusion. In this hobby, they pretty much cancel eachother out!
Pet stores will take big plecs as there are always fish keepers who look to buy larger fish - so for this reason, LFS will take it as they can make money on them. Further more, you could try and sell him...
Don't return your baby plec if you don't want to - It's up to you. They do grow fast though. I got mine as fry and he's about 3.5 inches now after a few months. But you could look at otto's instead if you want something similar...?
People here seem to have this idea of a massive tank with one or two fish in it - Despite what some people may think, This does not look good at all in my opinion. At the end of the day, Fish are in a way ornamental - and as such need to be nice to look at.
Just how I feel anyways.
