30 gallon is, in my opinion, too small. Your sump as to be able to hold the water that will flow in if there is a power break and also has to be a able to hold enought water so that you dont have to worry too much about evaporation. I wouldn't go under a 50 gal sump for a tank your size, and it would give you a lot more room for your heater, reactor, etc.
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