Aquarium Lights Heating Up Water

When setting up new fish tanks there’s a lot to keep in mind. Finding the right heater and controller to keep the perfect temperature is a step in the right direction but there is a bit more to heating than that. Namely overheating.

When summertime comes our heaters often get long breaks. The problem is our aquarium lights are never given that opportunity. While powered many lights can emit heat, some far more than others. For instance an LED light will often be warm to the touch as it gives off heat. If, however, you touch a florescent light you will quickly discover it’s as hot as a stove top! hanging these lights above tanks will cause the water temperature to rise, which is usually fine. During warm weather is when the aquarium lights heating up water becomes a problem.

How Much Heat Do These Lights Give Off?

In order the typical heat out put goes metal halide, mercury vapor, incandescent, power compact, full spectrum florescent and finally LED lighting. Metal halide is so hot that it is actually dangerous to handle as they will stay hot long after the power is removed.

With the lighting types all sorted there’s a few more factors that determine the heat your lights will be transferring to your tank. The first note is placement. Many large reef tanks will have these lights suspended over the tank with no lid. This allows the air to flow freely and cool off with the surface exchange. With that problem out of the way the lights can be closer to the water and allow for the most light to reach corals. An optimal set-up in most situations.

A more common set-up in the household is the aquarium hood with a light installed inside. This keeps all the heat in the casing, meaning more of the heat will transfer to the air between the light and the water, thus heating the water. A small amount will transfer into the hood and then the outside of the tank, but this will be minimal. These set-up are the ones that can really cook our fish in the summer time.

The set-up I prefer to use is a light strip placed above the tank with a glass lid between the two. This keeps almost all of the heat out of the tank while still allowing the light to be close. The use of glass between the light and tank does reduce the light that corals get but only by a small amount. More importantly it protects the light from mist and keeps the tank cool during hot summers. This allows me to run tanks year round without the use of chillers.

How Can I Reduce The Heat From Aquarium Lighting?

As previously stated my favorite method of reducing light heat creeping into the tank is the use of glass lids between the tank and the light. This combined with normal home temperatures or around 75 degrees is enough to keep my tanks cool. If more cooling measures must be taken here are a few tips:

  • Turn up the AC: While this may seem like a silly answer many homes with heated pets(fish, lizards and even birds) can find themselves with a higher temperature than the thermostat is reading. I first discovered this when my house turned into a frozen tundra. Turns out my tank was directly by the thermostats sensor so the AC was constantly on. If your tank is far away from the AC it may not even notice the heat.
  • Increase Aeration: This may seem a bit odd but by increasing the amount of aeration will actually reduce the heat. This can be done with filtration or circulation. Pointer power heads to make the water move more will keep the surface cooler and allow the water and oxygen to trade heat. This method does not work for hooded units.
  • Close the curtains: Silly right? Not at all. Often the solution to our problems is rather simple, we just don’t see it. When the tank is constantly hit by strong rays from the sun it will always rise several degrees. Not only that but even more algae will grow from the suns rays! Tanks are often meant to be placed away from the windows but just incase yours ended up in direct light, shut those curtains.
  • Use tank chillers: This is a bit more costly but if your tank is always too hot and your home is kept fairly cool there are few other choices. A chiller will always maintain the temperature just as a heater will, turning on only when the tank gets too hot. Once a chiller is installed owners never have to worry about overheating in the tank again!

There may be times when you need to quickly cool off your tank rather than apply a long term solution. This could be because a heater got stuck on or you left the AC off when you left the house. Either way here’s a few quick ways to get the temperature down safely:

  • Use frozen water bottles: This is a handy trick that can reduce the heat quickly and safely. Simply take a bottle and fill it with ice, cold water or preferably freeze it if you have time. Place these in the tank and ensure they have a tight lid to avoid adding untreated water to your tank. The cold bottle and contents will absorb the heat of the tank and lower the temperature without causing any additional evaporation.
  • Aim a fan at the surface of the water: Unlike the previous method fans will increase the amount of evaporation in the tank. If only used for a short time however this can be considered a non-factor. The fan blows cooler air into the water and stirs the water so that the same water is not always near the surface. Combine this with the bottle tip and the tank will cool rapidly. Just don’t cool it too much too fast.

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