What size tank is it. You will definately need to add a CUC, clean up crew, of snails and crabs and such. Are there any fish that you know that you are wanting down the road? Will your tank be a community tank, or aggresive. Clowns are a good place to start, and if you plan on two, get two now. It will make it easier down the road, but if your tank is only a ten gallon you can only add one. If you have a large tank and plan on aggresive fish, then the clown will be lunch.