No, but it has to be fully submerged at all times, and this depth may be risky since the water will evaporate. We would recommend making the water a little deeper, if this is possible, depending on the size of the turtle. Otherwise, be sure to monitor it closely and top the water off as often as necessary to keep it submerged. Additionally, it can be horizontal, but should be placed such that the turtle cannot reach it and it does not rest against gravel, etc.
Alternatively, you might use a heating pad under the tank instead. I've heard of some people doing that, but be sure to place it under the glass so that the weight of the tank does not rest on it.
Date published: 2018-04-04