I know, makes no sense whatsoever. I have a drainage layer in my RETF tank. I just noticed the other day, its fully up with water. I don't think its probably very good for the plants. In fact, I have one I can tell is rotting at the bottom and I'll probably lose it soon. So far I have stuck in a few extra pothos cuttings, in hope they help drink it up. I have also poked a few holes into the dirt, in the hopes the water evaporates out. My only other ideas is to put an under the tank heater on the bottom. I would hope it would cause the water to warm up and evaporate better. I can't dry it out with the lights, or I'll fry the frogs. So everything needs to stay moist. I have no drain in the bottom and wouldn't know about how to put one in without shattering the tank.