We swear by the purigen pillows. They remove all ammonia, ammonium and polish the water. They are also re-chargeable so after the initial purchase cost of around $30 you have something that should last year 10 years or more unlike the disposable activated carbon etc. All our turtle aquariums run with purigen in the filters as well!
where do you get this product?
also i am guessing you keep the tank water at a certain temp, however what happens if they want to cool down or warm up? how deep of a tank do they require?
also it would be interesting to see if they would enjoy a land area with a heat lamp and a lil vapor making thingy.
andrew