So apparently the water area in my grey tree frog tank has started leaking into the drainage layer and swamping my substrate. I noticed the last few days that the water level was dropping more than should account for evaporation, even with a heater running. So I took a peek at my drainage layer, and sure enough, it was about 3/4 full after only being "moist," no noticeable water level, just a week ago. So it's a slow leak, but a leak nonetheless, looks like that will be my unfortunate project today. Also realizing I need a bigger qt tank, my four greys are going to be pissed shoved into a 10 gallon for a couple days while I fix this.