Water Temp?

[Mentat]

3-4 in. of water on a 20 gallon can be too much volume for a heat lamp; unless room stays steady and the heat lamp is capable to slowly bring up the whole enclosure to desired temperature. If heat lamp is not enough or if below situation is right, you need a submersible water heater rated for the tank water volume in addition to heat lamp. Do not recommend using an under tank heater to warm up the water.

Not sure understand clearly; but if your room temperature varies due to A/C being on/off, you will probably also need a thermostat to control the heat lamp (water heater has own thermostat). Good luck !

[Amber Gyore]

It really depends on who you ask on the forum. A lot of members completely swear against underwater heaters, saying they are a waste of money and can actually endanger your frogs. I don't think they would actually do any harm to them, but personally I have noticed that underwater heaters are in fact unnecessary. My frogs thrive in 65 degree water, and I know that they will also be just fine in 60. Most underwater heaters automatically bring the temperature of the water up between 70-78 degrees, which is far too warm for these frogs. My frogs, although active, were very dark and always hid when I had the heater in the tank. Once it was removed, they became more social and their colours got brighter.

It's really based on personal preference, and I think also based on the frog. I would just watch your frogs and see if they are happy in the climate they are in now. If they are active, bright, and eating, then there is no need to add additional heat to the water.

Besides, slight fluctuation isn't going to hurt them any.