I have a pleco and 2 goldies in a 30 gallon tank. I am worried about when he grows too big. I hear I will need a 50 gallon tank for one. I don't have space for a larger tank. He is already 6 inches long and seems happy with the fan-tailed goldie and black moor. HOw much longer before he is too big and what do I do with him when I can't get a big enough tank. Can you give them to aquarium stores?