This is sump v2 (18 gallon tall tank) with higher baffles and an eggcrate stand for the skimmer. We added an auto-topoff today (the small tank, roughly 3 gallons) with a float switch. (Note: we later replaced this with an All-Glass 7 gallon bowfront, the largest off-the-shelf tank I've found that will fit in there with the 18T sump.) On some days we lose almost a gallon of water a day to evaporation (normally more like half a gallon) so now with the topoff we can leave the house for more than 12 hours at a time without fear of a pump running dry.