Welcome to FishLore! It's great to have you with us! You probably have a common pleco, and in reality, they need at least a 55 gal. tank! You might be able to trade him in for credit at your local fish store, and use the credit for 4 more neons.
If you don't already know about the cycling process, please check out the sticky called FishLore Articles for Beginners. Cycling is a very important concept you must know to be successful in this hobby. Also, a 5 gallon tank is harder to maintain than a 50 gallon tank, because you have less water to work with to keep it stable. You should be commended for the great job you have done so far. Your pleco should have died long ago, but because of your care, he is still with us.
I'm also gonna move this thread to the beginners forum for more exposure!
