Return Area Size

[seanb]

I , am planning to upgrade to a 225 gallon tank and a larger sump to go with it. My question is how big should the return area of my sump be. Yes I know the larger the better, but how much water can I expect to lose from evaporation in a tank this size?

 

[pheinzig]

75g would be a good size sump.

You can do a covered sump/DT to reduce the evaporation.
Depending on lighting and your typical California weather....
Id guess 3-4 gallons a day under metal halides. Just have a fart fan or something blowing air out of the room and you're gonna be good.
I have a 4.7w, 5" fan that keeps my aquarium room happy.

 

[seanb]

I was actually planning a 90 gal sump, but of course it would run only half filled and only about 1/4 of that volume will be in the return area. Is that enough? I will have an ATO, but what if something goes wrong. That leaves me with about 10 gal before the return pump would run dry.