I don't think water volume alone is enough to determine chiller requirements. Ambient temps, exposure to heat inducing lamps and pumps, humidity levels, and surface area all effect the heat load, There are probably factors I haven't even thought of. I would suggest you try this: Set up your system as it would normally be operated, pumps, lights and all. Run it for a minimum of 24 hours. At least until you get a 4 hour period where the temps no longer are rising, but remain stable. Check it during the warmest part if the day. This will give you an accurate idea of how warm your system will get. Get a chiller(s) that can cool that water down to the temp you want to be at in 4 hours (I'm guessing here, anyone got input?) This is probably a little more than you need, but thermostic control will prevent over cooling and better too much than too little. My 1/4hp chiller cools my 50 gallon ebb-n-flo and runs very little also, but a DWC would probably heat up more due to the pump running all the time. Sorry about the troll remark. I shouldn't question the motives of those coming here to ask for help.
