Today I was looking at my cramped aquarium closet and realized that I really have no need for a large top-off reservoir. The old reservoir was a 3 gallon bucket and just took up too much space, so out it went! I decided to make a new one that's much, much smaller. In fact, it's smaller than a shoebox-- just big enough for a float valve and a tunze osmolator pump! I'm loving this new setup so far. It provides the safety benefits of my old setup (DI filter is not connected directly to the sump, so a failure won't flood the tank with freshwater) but it requires way less space. I'm considering building a new sump soon and may build this into it near the back, with an added safety overflow outlet that drains somewhere safe. By the way, for years I've used a sediment filter, carbon block, and DI resin but not RO. With our excellent water quality here I've always found that DI does a great job and lasts plenty long by itself. RO just isn't worth the hassle for me. Curious if others do the same thing?