Marineland Visi-Therm Aquarium Heater, 25-Watt

Have only had this about a week and so far, so good. I have it in a 5 gal aquarium housing Red Cherry Shrimp. It's a little bulky for a small heater, but the wattage is about right for a 5 gallon tank, sure wouldn't want any more. Set on 70 (which is what I'm calling half way between the numbers 68 and 72 on the heater dial), it keeps the tank water at 72 to 74 degrees when the room temp is about 70 degrees. You'll probably have to play around with yours to get to know how it sets, and the setting may need adjusting if the room temp varies alot. Just be sure to have an accurate thermometer in the tank. (I set mine up and tested it in a tall pail of water prior to putting it in the stocked aquarium.) The heater comes with a detachable bracket with 2 suction cups, the suction cups stick very well, and the heater stays in place once mounted on a clean tank wall. The heater must be mounted vertically and requires a minimum of 6.5" water depth ABOVE THE SUBSTRATE (heater cannot touch the substrate or tank contents/decor). A standard, rimmed 5 gallon aquarium will allow 9" of water depth with no substrate and filled to the very top. Hopefully, that gives you some idea of how deep a tank must be to accommodate this heater plus your substrate. For $14.74 delivered, it seems to be a good little heater but I wish I'd have seen this one first, mostly because it can be mounted vertically or horizontally.  Cascade® Heat® 7" Aquarium Heater 25 Watt for 5 Gallon Tanks  I can't say I dissatisfied with this one, though, so I'm giving it 4 stars. Should something happen to change my mind after using longer, I will update this review accordingly.

I currently have one in my 29 gallon community tank. This is the third one I've had for this tank. The first one got water inside and stopped working. Marineland customer service was great and sent me a new one that arrived cracked on the bottom so they sent me a third one and has been working great ever since.I have it set at 82 degrees and it is consistently 80 degrees on the opposite end of the aquarium where the thermometer is. It is very sturdy but a little bulky.

Be careful... The temperature on the heater is not accurate, so if you set it to 79 degrees you will cook your fish as it will heat up the tank to 86 degrees. I currently have it set to 72 degrees and the tank is 79 degrees according to the thermometer I have in the tank.

First let me say don’t waste your time with any other type of heater. The Heater has just adjustable controls on the top, based on temperature as well as Fahrenheit and Celsius temperature indicator on the heater to tell you what temperature the tank actually is, as well as a light to indicate that the heater is in operation. It also comes with a suction cup mounting to stick to the side or bottom of the tank glass or plexiglass. Only fault is the slightly stiff cord. Comes in many Wattages, so size appropriately.

I've used this thermometer in a 2.5 gallon acquarium for about a month now. It does a good job of keeping the water temperature fairly constant but I have the setting at 72 and the water temperature reads between 77.5 and 80 degrees, so the calibration is off. I would still recommend it for a small fish tank but make sure you check the water temperature with another accurate thermometer.

Compact, which is what I was looking for. Seems it is always on, even in my tiny 8 gallon nano.

This heater did not work right. I put it in the tank and the next day my fish were dead because it overheated the water. I would not recommend this.

This is a perfect heater for a small aquarium. I have purchased two, both for 3 gallon filtered betta tanks. The heater maintains a steady, accurate temperature, and my fish are very happy.