If you've adequate air going to your roots, there is no problem with letting your water level stay right below or even touching the botton of your netpot. I leave mine this way. This avoids those nasty looking coord roots and gives your roots a larger space to grow and inhabit. Like you, I run standalones and their biggest downside is that their PH will swing much more frequently, and you have to add back water (and nutrients along with it to maintain ppm's) a lot, in mid flower I oftenly have to add back 1/4th to 1/2 of a gallon to each bucket everyday. But it's worth being able to tailor each plant's res to their needs. If you don't intend on buying a water chiller, I would look into getting some beneficial bacterias. I very oftenly get water temps at 72F or even higher and have never had root rot running beneficials. Like Hydro4life mentioned, it may be worth looking into larger air pumps, but that really depends on how many buckets you're connected to. If you've just 1 or 2 buckets, it's probably good to go. But if you're running 3 or 4, that may be a different story. I know setting up is a pain, but it is so worth it when you find your groove