depends on how long it sits there... if it is drunk quickly, it's fine.
could use those pot risers/elevators and drain out bottom in future, if you wanted. but, this sort of thing works well. it's kind of a small hempy bucket or whatever they call them. just a smaller reservoir at bottom.
so does the drip run continously? if it is a pool of water at all times in that bottom 1.5", then stagnating water is an issue. if the drip refreshes it enough, that would mitigate it. bubbles wouldn't hurt, but not sure how much it'd help. it'd be less about O2 and more about agitation to reduce microbial growth.
