Do Aquarium Lights Heat Water? (4 Tips for Controlling Heat in an Aquarium)

Aquarium lights are almost a necessity in a fish tank. They provide light energy that is necessary for the growth of plants and they allow you to more easily control the light in your fish tank.

However, some aquarium owners raise a valid concern about aquarium lights heating the water in their tank.

To answer the question, aquarium lights do heat water. But the amount of heat generated by the light varies depending on the type of light bulb used.

This article will go into detail about the heat generation of the different types of aquarium lights and the best light choice for fish tank owners.

Will Incandescent Lights Heat an Aquarium?

Incandescent lights used to be the most common type of light used to light an aquarium. They have recently fallen out of favor due to advancements in lighting technology.

For those that don’t know, incandescent lights are the traditional lightbulb that you see in cartoons. They have a glass enclosure and produce light by heating a wire filament.

They aren’t very efficient as they only convert 10% of electricity into light. The rest of the electricity produces heat.

This means they will heat your fish tank up very fast. I

I do not recommend using an incandescent light to light up your fish tank due to the excess heat produced by the bulb. They are also much less energy efficient and have a short lifespan, so it will cost you more money in the long run.

Will Fluorescent Lights Heat an Aquarium?

Fluorescent lights convert about 20% of energy into light and 80% of energy into heat.

They’re slightly more efficient than incandescent lights, but still not particularly good. They’re still a popular option for fish tanks because of their low cost to operate, slightly better efficiency, and longer lifespan than incandescent lights.

They were the most popular option until LED lights became somewhat affordable about a decade ago.

Personally, I don’t recommend them because LED lights are just so much better and not really that expensive these days.

Will LED Lights Heat an Aquarium?

LED lights will heat the water as no light source is 100% efficient at converting energy into light. However, they produce so little heat that it’s not a huge problem unless you have a large amount of LED lights and leave them on for extended periods of time.

I don’t recommend doing either of those, so it’s not a problem.

LED lights are my top pick for lighting an aquarium. They’re relatively cheap, last about 10 years with proper maintenance (ie. no overheating), don’t use much energy, and produce very little heat.

The only downside is they don’t produce light that plants can use from photosynthesis. If you have plants, then a full spectrum LED light is your best option as it has the full spectrum of light required for plants.

4 Ways To Control Heat in an Aquarium

Heat can become a problem in a fish tank. Most owners have little to no understanding of just how much heat a non-LED light can produce, which will drastically alter the climate in your tank.

Managing heat in an aquarium is absolutely essential to keep your fish healthy. Even tropical fish can’t live in water above 85F, so it’s something to keep in mind. And it’s even more important when you have colder water fish like goldfish.

Anyway, here are some tips on controlling the heat in your aquarium.

Lights on a Timer

First, you want to keep your lights on a timer or simply turn them off at night. The sun isn’t out 24 hours a day in most of the world, so you have no need to keep your light on for 24 hours.

It will also keep your tank from overheating, which can become a problem if you use a fluorescent or incandescent light. It’s less of a problem with an LED light, but can become problematic if you leave your LED light on for days at a time.

I recommend using a timer and keeping the light on for 10 to 12 hours. That’s enough time for the fish to be comfortable and any plants to grow.

You can also use a dimmer on a timer to more closely mimic sunrise, sunset, and cloudy weather, which all occur in nature.

Keep The Aquarium Out of The Sun

Next, you want to keep your aquarium out of the sun.

A lot of people put their aquarium in a room with a big window that gets a lot of sun.

That’s really for two reasons.

First, it will be annoying to regulate the temperature in your tank as the sun will heat it up in the day and cool it off at night.

The other problem is you will get overrun with algae if you live in a sunny place like Florida or Arizona. The sun produces light waves that algae love and you can’t turn off the sun.

I speak from experience on this one – don’t put your fish tank in a sunny room in your house or you’ll be overrun by algae and struggle to maintain a constant temperature in the tank.

Put a Fan Over The Tank or Use a Chiller

If you are really struggling to keep your tank cool, then you can purchase something called a chiller.

Basically, a chiller will pull heat out of the tank and dissipate it out the back of the tank. It works similarly to a refrigerator. Just make sure that you have good ventilation or else the water will absorb the heat, which will defeat the purpose.

A more rudimentary option is to simply point a fan at the top of the tank. It’s a little ugly, but it works perfectly fine. The fan will blow cool air onto the top of the tank and cause a little aeration that should help dissipate some of the heat.

Use LED Lights

Finally, use LED lights to light up your fish tank. The benefits include better energy efficiency, a significantly longer lifespan, and very little heat production.

If you use LED lights with the other tips listed, then you should have no issues with heat in your fish tank.

Closing Words

To summarize, all types of light emit some heat, so they will all heat up your fish tank. I recommend using an LED light as they emit the least heat and last the longest.

You can also use a chiller or point a fan at the surface of your fish tank to further reduce the temperature if you are really struggling to keep your tank cool.

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