Hello: I am just about finished on my live rock cycle as my nitrates are down to 2. I have a 20 gallon high tank with basically three levels gravel bottom one layer about 1/3 up the tank and another layer about 2/3 up the tank. I have a cave in the middle. I need to post a pic and will do so tommorow. I am at a loss as to what to get I like color and since this is a small tank size matters. I have a 130 PC with actinic and 10K and 70 watt MH. I do like Zoo's though!