Pros: Heats up a much larger tank than specs say; given me no problems.
Cons: Honestly can't think of any.
I have a 58-gallon aquarium, and found that the old heater that I had was keeping it heated a bit higher than I wanted for the fish I had (78 degrees for goldfish), and there was no way for me to adjust the heating levels. So I went to my local fish store and bought a 50-watt Top Fin aquarium heater. Be aware that the packaging says that it heats up to 10 gallons. I kid you not my aquarium is 58 gallons and this unit keeps it a nice, comfortable 73 degrees all the time. I have it turned almost all the way to the LOW side as well. Honestly I know that all the heaters are ranked according to wattage and aquarium size, but I’m sure glad I didn’t shell out 45 bucks or more for a heater that specifically said “up to 70 gallons” or something like that.
I have no intention of finding out how hot it can get my aquarium going, but there’s no doubt in my mind that the vast majority of fish you would buy at a local fish store would be just fine with this heater, in any aquarium up to my size.
It has an attractive grey plastic covering for it. It has an orange light that tells you when it is on; after a certain point (depending on what level you set the unit to heat up to), it shuts off and then on again. I’d buy this again in a heartbeat. I’ve had no problems with it at all.