Just because you can set the thermostat on your heater, you still need a thermometer to measure the temperature! Unfortunately, heaters can fail. They can get unplugged or even get stuck on heat. That’s bad! Avoid using an oversized heater. For aquariums larger than 60 gallons, it’s good to use two smaller heaters set to the same temperature. If one dies, usually the other keeps the temperature safe. For most home aquariums, 3-5 watts per gallon is the simple rule of thumb. For example: A 29 gallon tank would need a 100 – 150 watt heater.
Learn a great habit. Check the temperature every time you feed the fish. Get a nice thermometer that you don’t want to hide. Digital thermometers are easy to read. The ones that store the minimum and maximum temperature are really useful, that way you can see how far the temperature varies each day or each week.
20 gal/75 L, 50 watt, 75 watt, 150 watt.
There are two things we need to establish here, the size of your fish tank and what temperature setting you are trying to achieve. If the tank is large then you may require a larger heater, the 150 watt heater that stays on is struggling to reach the pre-set temperature. Never use a time with the heaters they need to be switched on 24/7, if you post the size of your fish tank we can advise the correct heater rating that you should be using. ✍ Share your opinion or experiences regarding this comment
Top 5 Best Aquarium Heaters - Fully Submersible With Thermostat
The heaters comes with a lifetime guarantee. It offers aquarium heater sizes in 50 watts, 100 watts, 150 watts, 200 watts, and 250 watts. They includes two clip on suction cups that allow it to be mounted anywhere in the body of a small fish tank or a large aquarium. It sticks well to both glass and acrylic aquariums.
It's vital that you measure the water temperature in your fish tank