They term overstocked refers the bio-load and size a fish will reach. 1 ipg is a starting point, that people use that is simple to understand but what he did tell you was it was for the adult size of the fish. When you get into some fish require more space than others, some hang out at differnt levels in water. Some fish make more waste than others.... the pleco you have creatate alot of waste, to the point I seen them clog up an intake on the filter, with waste. On the other hand some fish its almost nonexsistant, like the oto cat (which are a small algea eater only grow to 1/2 to 1 inch). you should go and get your self a complete water test kit. So you can test your water daily....

__________________
Gold Coast Aquarium Society South Florida
www.goldcoastaquarium.org