Aquarium heaters are important because you have to maintain a constant temperature range in order for corals and marine fish to survive.

Typically the outer limits of the safe range are in the area of 74°F to 80° range Maybe up to 83°F for short periods of time. But for long periods time you need to stay as close to say 77 to 78° as possible.

Optimum Temperature Range for Reef Tanks

We like 77 degrees F as an average temp, because it gives you more room on both sides if there's a mistake to be made. You have plenty room if it overheats a little bit and plenty of room if it gets a little bit cold.

So we shoot for around 77 degrees F, and the corals seem to do better. At higher temperature, you have less oxygen in the water and it can stress out the corals and stress out the fish even more.

Coral Bleaching from high temperatures

In nature, what you find is the higher temperatures can cause corals to become stressed and it can even cause an event called coral bleaching. Bleaching occurs when the stressed corals expell their pigmented algaes called zooxanthellae. Corals can bleach even in 85 to 90° temperatures, particularly if the current is low or stopped. Entire reefs have been reported to bleach out due to higher temps and low current. And as global warming kicks up even more, I think we will see this more often, sadly.

Once the coral bleaches or expels its algae then it is very difficult for the coral to recover. This is because it has lost one of its principle food sources, the simple sugars produced by photosynthesis.

So we recommend you try to attain a temperature range of around 77 to 78° and the way to do this of course is with automatic tank heaters.

Common Heater Problems

One thing we noticed about a lot of the heaters on the market is that they don't seem to be that accurate or reliable. We haven't really found a heater that we really like. We have tried several major brands and they all seem to die after a season or two. We can often see a break in the heating element or a spot where it has burned through. I wish I knew what caused this to happen and how to prevent it, but I think its just inherent in these types of heaters.

Another common problem we have with heaters is that they don't turn off when they reach the temperature we have set them to. Obviously this can cause a problem with overheating the tank. So be aware that this is a possibility with tank heaters. Sometimes they just don't turn off.

On the other hand, a lot of times when it's too cold, the heater doesn't turn on, even though it's colder than temperature is set to.

So we would love to find a heater that's much more accurate and reliable. Let us know if you know of one.