The reason I ask about tank size and skimmer is b/c I have a 120 with 2 400 watt MHs and with 2 8 inch desk fans I can only keep the temp at 84 degrees if the tank starts out at 78/79 in the morning. That is a huge temp difference and it is winter here right now. In a few months the temp will go up to 90 (outside)on average and sometimes pushing 100. In the summer sometimes its so hot my A/C has trouble keeping the house under 82/83 and the A/C runs all day. To make a long story short I guess I have no choice but to get a chiller.