I think that it is probably not suitable for the tank. Whisper heaters have worked okay for me, but I had no other choice at those times and I bought them rated at 2.5 W/gallon for their tanks because I wanted to keep them in range. I don't know how well they work when they are overpowered for their tanks, nor do I wish to find out if there's a better product out there, like the Hagen. (I've never seen a Whisper rated better than a Hagen of the same power.)