im using the tetratec pf300 with the heater. i have noticed that as time goes it declines in its efficiency to heat, but i have found that once you clean it as gunk will build up on it, that it works very well. try washing it once you notice the water temp drop. it still dosen't do what it claims about warming the water all over. the right side of my 55gal will be 80, and the left side will be around 83, while my heater is set for 84. i just have it set for 84 so i have a decent medium between temps. all temps are F.