2 gallons of water per 1/2 inch fish?
Is that 4 gallons per 1 inch of fish?
A 10 gallon tank could have 2.5 inches of fish total?
Seems very conservative for an established tank. (The old rule used to be 1 inch per gallon, but I always thought that was asking for trouble.)
Maybe shoot for somewhere in between?
Here's a reasonable take on the rule of thumb:
http://freshaquarium.about.com/cs/qa/a/qa016.htm
BTW, subzero, you might be looking for a new home for your bottom feeders if they are plecos (Plecostomus). These suckers will grow and grow. Big fish use up oxygen and make lots of fish crap. Keep an eye on it.