What about a system like pot-in-pot drip irrigation systems used in plant nurseries? I think they use pretty low pressure and flow, so should be pretty cheap. Pretty much a flexible main tube with lots of smaller tubes distributed along the length, each going into a pot. Set your pump up to pull from the bottom of your terrarium, put it on a timer, and boom, instant "recirculating bog" right inside your grow case. Then, once in a while, just swap hoses at the pump output, turn the pump on, and you can drain the grow case reservoir right into a bucket, and refill it with fresh water. I could try to draw a diagram, but I'd never be able to upload it from work. You ought to be able to get a small pond pump for a system like this for about $30. Maybe another $30 in tubing, nozzles, etc. Or maybe I'm way out in left field...