I liked how I put it bottom piece of glass and put gravel around it but let about 1/4 inch exposed so took very little room in already full tankWHAT I LIKED ABOUT REBIRTH SUBMERSIBLE HEATERS TEAM IS THAT THEY WENT OUT OF THEIR WAY TO CORRECT ISSUES WITH HEATERS WITHIN A COUPLE OF DAY AFTER I DID A REVIEW. I THANKYOU FOR YOUR GREAT EFFORTS.FERNANDODied after a month and took several fish with it. I find that most of these cheaper, made in China heaters don't hold up. I had it just long enough so that I couldn't return it.I have not used this much yet, but so far it seems like a good heater. I needed it for a smaller sized tank, and it does well with that. It is fairly small so does not take up a lot of room or need a taller tank. I am not sure how accurate it is as I had issues getting the type of thermometer I wanted, which is why I am not using it much yet. It came well packaged without any damage.Right now it is hard to tell how well this really works. Since it is summer my house temp is above normal (75ish) so this water heater doesn't need to work as hard to keep water warm. I put the heater (50w) in a small amount of water (maybe a quart) to test and it heated it up a couple degrees until it went to 80ish. When the light is red it means it's heating when it's green it's done heating at that time. I'm not sure if it has an internal thermometer that will stop heating it at a certain temperature or not, but I plan on using this for my ducks in the winter to keep their water from freezing outside. It says not to use in freezing temperatures but this was in the manual after I got it so I will just try it anyway. So like I was saying earlier I think the performance depends on different factors including how much water you are heating and your room temp... I think I will update this review once it gets cooler and see how well it works then.Only had for a weeks and it BLEW UP IN MY TANK AND SHATTERED ! !!