HITOP Compact Submersible Aquarium Heater -100W Digital Heater for Fish Tank Turtle Tank 10-25 Gallon, Saltwater and Fresh Water with Temperature Controller (100W)

I was skeptical because the only aquarium heater I ever trusted and found that works good was a good old fashion traditional glass, electric internal element and boring dial heater. After reading reviews I tried this one to use in my 100 gallon pond which has my small Koi and lemon plecos in it. I like to keep them cozy during winter plus I have lemon plecos in there too who keep the pond very clean, this set up works well in North Florida. We can get a few 40 degree days/weeks in winter but this sand heater helped keep the water at 68 degrees during those days/weeks. I could put another 200 or 300 watt in to reach 78 degrees for the lemon plecos when it's 40 degrees outside but it's unnecessary. Everyone does fine at 68 for a short time.The built in thermometer works pretty good too. The sand in the glass is an unusual way to heat and I didn't know what to expect. It is working very well and consistent in the auto on and off at temp setting you prefer to set. I got 2 of these 300 watt's one is in a 75 gallon aquarium and the other is in 100 gallon pond outdoors.As small as it looks it gives a big and quick heat up at your chosen setting. I was surprised how well it works and fast.The only thing I am being careful about and worry is the digital external compartment that's built into the cord gets very warm and I don't know if it is water resistant or not or that if it could catch fire being this compartment gets so warm/hot when heating is on. So my advice is be careful where you place that external piece. Maybe hang it and cord off the aquarium rack somehow or something so it doesn't get wet and be sure that compartment is not up against any carpet, wood or Sheetrock walls, always think SAFETY FIRST when it comes to aquariums and where to place things.

I decided to replace my old 50W heaters in my 7.1 gallon tank because the numbers had come off and I kept smelling a “burnt” smell near my tanks. So I ordered one of these 50W heaters and wow they are so small. I was actually worried they wouldn’t be big enough to heat my tank to 79. But it does the job well! I included a picture of the heater next to a BIC pen for scale. The cord is a bit short so if you need it to reach far you’ll have to get an extension cord. The heater comes with a digit temperature “setter”. The range is from low 60s all the way up to 90 degrees Fahrenheit. It comes with three suction cups (I don’t think you’ll need more than two, but it’s nice they include a third just in case). In the box there is also an external adhesive thermometer, which I didn’t need, but again, nice to have.I liked it so much I bought another! As far as durability, only time will tell. I’ll update my review if I have any issues with these holding up.

Good value for a small heater, it works for my 20 gallon and the temp reads spot on for what I set it to. Can be fully submerged for proper placement and effective heat dispersion. Not as fancy as some other name brands but it does what it advertised to do

So I have been using this heater for a while now. It came with a manual, but it was not well written - which is common in foreign brands. There is only one button. Single press will change the temperature setting. Every time you press the button, the temperature setting goes down by one degree, and then goes back to high temperature again once it reach minimum temperature. Once you see the temperature you like, leave it and the indicator will start to show current water temperature (not the set temperature) and it will start to monitor and heat the water when necessary. When the heater is on, you will see the red light next to the temperature indicator. You may want to double-check this temperature setting when using for the first time as I set my temperature way high without noticing about it for the first round (almost killed my fish).I like to monitor my water temperature in celsius and this is the reason I bought this heater. How to switch from F to C was no where to be found. I finally found similar product in the web and learnt that by pressing the button for long time, it toggles F and C. So that was great for me.I have relatively low water flowing tank, so reading the temperature indicator is bit tricky. When the heater is on, it shows bit high temperature because it is measuring heated water directly. So it would be better if you have good water flow in the tank. Never the less, water temperature remains to be stable with this nice miniature heater.I give one-less star for poor manual, but product itself is good.

I’ve been using this heater in my nano tank for over a year and it’s still working great.

Had it for a few months then it stopped working.**edit to review: seller contacted me and offered to refund or replace this item. I am changing my review to reflect the fact that this seller is dedicated to making sure we are satisfied with our purchase(s). I appreciate them for reaching out and offering to resolve the issue I had!**

Update: I reduced the rating to 1 star because the seller reached out to me only to blame me for their products issue. They tried to say I had set it on Celsius. I did not. It had been running for a week at 77 just fine. I had not touched it when all of the sudden it was up in the 90s. I bought 2 of these heaters and I know how they work. Both were set on Fahrenheit. The digital display went crazy when the heater got too hot and the numbers were reflecting weird. Besides if what they were saying was accurate, that I accidentally set the heater to Celsius, that is also a defect in their product. It should not reset so easily that I wasn’t even aware of the change. I would have noticed the display change immediately too. Sorry, but this product is a fish boiler piece of garbage. If I could rate it lower than 1 star, I would.Initial review: bought 2 of these heaters and one worked great. The 2nd one, the temp controls went crazy. It showed 33 which is not supposed to be a setting. The actual temp in my aquarium was 92. Thankfully I didn’t have any fish in the tank yet. Would not recommend these especially in a small tank where the temp can easily swing. Tossed both and ordered new different brand heaters.