Well, if your sig doesn't lie - you already have an overstocked tank. I can tell the bacteria are crying right now
You will need to do pretty frequent water changes.. Find out a safe amount where you can change a relatively large 30% or so without lowering the water level so much as to harm the fish. Or you could do several changes for a week or two for it to balance of about 1 gallon then just do a normal cleaning.
What water conditioners do you use, how much do you have in the way of decorations, etc..?