Hi Jason,
Nah they dont absorb water, but I removed mine because I add a handfull of crix
at a time so the frogs can hunt and the crickets ate the wall!
Unless your breeding them (there breeding size/age) theres no need to have so much water. Another prob with that is how you make the land area. I found large smooth white pebbles easier to remove and change water. If you have upright branches sitting in water they grow funky mould below the water, Yuck.
You shouldnt need the heater all at this time of year, its warm enough for them, (if the normal temp is above 20c)
Im just using a large waterbowl, which is easier to clean daily and gives them more floor space.
It will depend on the size of your frogs how much they eat, and the time of year.
right now mine are eating maybe a doz crix and a handful of woodies each every few days, but mine are adults.
The easiest way to see how much there eating is first eliminate places where food can hide as much as possible. (crix n woodies will hide behind that wall.)
Put in as many as you think and see how fast there eaten. This way you can add more or less as they want.
Also, if you leave food in for them to hunt, leave fresh carrot and/or some greens for the crix/woodies to eat, this way there gutloaded, and wont bug the frogs whil;e there sleeping in the day.
P.s in winter you should only have a shallow bowl of water (change daily) when its cold, humidity should be much less or they will get sick. They wont eat much when its cool either, so in winter dont leave food in, just offer so many every week or so.
If thetre young frogs keep them warm in winter ambient 25c, but dont heat water (humidity) use a heatmat on the floor (not under waterbowl) or a small wattage lamp above (outside) the tank.