Hi, My name is NIck. My fiance and I are planning on buying a 20 gallon tank today for our son. We will be buying a 20 gallon tank. We are looking to get a blue lobster "crawfish". We herd from a few places that if we do that we are limited to getting a few fast moving fish that swim toawrds the top. IVe asked. and each place gives us different answers that contradict eachother. So here I am What kind of fish Can I get and apporx. How many fish can I put in the 20 gallon with the blue craw. Also I will be purchasing the tank today and setting it up to run overnight to clean out the dirt and dust from the tank and the gravel. Also we Will be putting in plants. Are the plan ts something I can buy rightaway and put in the tank today, or should i wait for tomorrow when we go buy our stock of fish to put in?