EDIT: The manufacturer contacted me a few weeks ago to try to remedy the situation. After I returned these I ordered another brand that was able to heat up my tank to about 82 degrees. I told them my situation and what I expected. They sent me another heater and I placed it in my tank. I didn't see any noticeable change in temperature so as far as I was concerned, it was not strong enough. I told them about my experience. Their only response was, "Sorry about that."Fast forward a couple of weeks... I set up a 20 gallon quarantine tank and decided to put this heater in it. It was able to heat up to 90 degrees so I'm amending my review to 3 stars. The only reason why I'm not giving it more stars is that another brand of heater of the same wattage, 1 heater, was able to do what two of these couldn't do. It's good for smaller tanks but not larger ones.ORIGINAL REVIEW:Won't heat up my large aquarium. I have a 220 gallon aquarium that I needed to heat up quickly to at least 84 degrees because I had an outbreak of ich. I already had another 300w heater that could only heat it up to 76 degrees so I decided to buy 2 of these to help out. I placed the 2 of these on opposite sides of the tank and I'm not seeing any changes in temperature. I have them set to the maximum and even adjusted it up and down a little to see if it will kick start it a little to no effect. I see the heating coils turn on every now and then but never long enough to make a difference in the temperature. I know my tank is large but you'd think adding 2 of these to one already in operation would make a difference but it doesn't. I'd love to hear from the manufacturer.My significant other is a teacher. Had a tank in her class room. The pandemic hit and we spent some amount of money to save her classroom fish (gold fish - 2 that have grown to about 6" long) in a 55 gallon tank. 72f is as low as it goes. I'd like 70 or even 68 to give it some room to warm during the summer is one down fall. BUT it keeps the tank at 72 while it is 65 in that room which is as cold as it can get unless a window get's broken or something crazy. I've have had it for 4 months or so. Seals seem ok, as my last heater got water inside it just after return policy expired. For topicals or salt water and you have a 55 gallon tank or a bit larger. This heater works well.Has worked well for a long time now. The cord is frustratingly short. I needed an extension cord to plug it in.when AC power is applied it’s ON continuously but it will not always show it. The only time the indicator comes ON is when the internal thermostat triggers the heating element ON, but it will cycle ON and OFF while the tank's water Temp is slowly rising. So far it’s taken 12 hours to bring my 20 gal tank up slowly from 62 to 75 , and it’s set at 80 so it still rising. The ON indicator cycles ON for about 5 minutes then OFF for about the same. This behavior and duration will vary a lot depending on your room temp, water flow around the element and tank size. I think this slow rise is fine since it’s very cool at night in my house at around 58 to 60 in the house and I don’t want rapid temp changes that are hard on the fish anyway. I wish it were easier to see the temp setting and twist the adjustment knob but I’m very happy with it otherwise so far. I expected the wire element to glow Amber or red but it doesn’t glow at all so aside from the ON indicator and a separate floating glass test tube lite thermometer ? I can’t see if it’s working.Purchased in early spring. Worked for a few months until the weather was warm enough that it didn't need to come on. Now that fall is here, my aquarium is 68 degrees in a 68 degree room and the power light on this heater has been on for 3 days straight. Good for a quick fix I suppose, but doesn't seem to last long.EDIT: Sent the seller an email. They apologized and sent me another unit very quickly. It's the same power rating, but definitely a different heater. We'll hope this one lasts longer. A+ for good customer service.So far this has kept a pretty consistent temperature. However, I bought this model since it has the protective plastic cage. It's being used in a plastic tote converted into an indoor guppy pond so I didn't want the glass to come into direct contact with the plastic container. The heater does not fit properly into the 3 piece cage, it's not quite long enough(the cage). You can eitehr use the entire cage, but not see the power light to tell if it's on OR you can not use the upper most section of the cage so most of the heater is covered AND you can see the power light. Since I need to see if the light is on to tell if it's powering on I opted for the latter set up.Comme la majorité des chauffe-eau ne vous fiez au niveau de température, mais bien à votre tthermomètre ou raccordé à un thermostat électronique, car placé à 26c la température à monter à 29.6c je vous conseille plutôt d'acheter en magasin ces pas plus cher et on a une garantie.Good heater...already had one but still order a 2nd because i like it.Package got stolen... contact the seller... no answer, im sad.Felt like writing it._______________________________________________________*update got refound when i ask, winter is coming so im ordering again ! *The thermostat in the heater did not work. It heated my 150 L aquarium to 32 Celsius (85 F) regardless of the chosen setting, even when set it to 22 Celsius (70 F). Perhaps it was just one defective unit of many but I am not willing to try a second one.Réchauffer l'eau de mon aquariumThe temperature control isn't great to read and set, but works to keep the temperature fairly stable