Chillers: What HP to Get?

[Aquattro]

On that size tank, if you even need a chiller, the smallest you can find will probably work. Depends on whether you turn your house heat on during the summer
You could even reverse your lighting period while you're gone, have lights on in the cooler hours at night. But I've used a 1/4hp on a 180, you don't need anything that big.