aquarium temperature

Controlling High Temperature in Reef Aquariums

Controlling High Temperature in Reef Aquariums

Reef aquarists are focused on providing their fish and invertebrates with the best of care. Much effort is spent maintaining water quality, lighting and water movement. Ideal water temperature is an area of debate, but most reef aquariums are kept between 76-83F. Reef keepers often find their water temperature creeps up during the day, exceeding these recommended temperature levels. What to do? We’ll take a look at the importance of water temperature and how to keep your temperature under control.

The Effects of Water Temperature on the Reef Aquarium

Fish, invertebrates and even algae are “cold-blooded,” meaning they cannot regulate their own internal body temperature.  A more modern term is poikilothermic (poy-KEELO-thermic). The metabolic rate of fish, inverts, and algae are controlled by the water temperature. As the water temperature rises fish will need more food and oxygen. Algae will take in more carbon dioxide and nutrients. Corals will use more calcium and alkalinity as their growth rate increases. Increased feeding and growth also means more waste products will be released, like ammonia and organics. Water, however, holds less and less oxygen as the temperature rises. Many of the biological waste-eliminating bacteria need oxygen to do their work. Picture this scenario. A warm reef tank causes aquatic life to grow faster, use more oxygen and produce more wastes. At the same time, the warmer water can’t hold enough oxygen to support the fish and invertebrates or the waste-eliminating bacteria. Obviously, this is not a sustainable situation. The water temperature should be stable, in the optimal range and not over-heated. On the other hand, if the water temperature is too low or frequently dips below the optimal range, the entire aquatic ecosystem goes for a “metabolic rollercoaster ride” as the temperate rises and falls. This is a stressful situation that can inhibit the immune system and lead to health problems in fish and invertebrates. The idea situation is a relatively stable temperature throughout the day-night cycle with minimal fluctuations.

aquarium temperature

 Causes of Overheating in the Aquarium 

The technology we use to recreate the reef environment will add heat to the aquarium. If you have a water pump, submerged in a sump, it is adding heat to the water. The pump is designed to shed excess heat into the surrounding fluid, which happens to be your aquarium water. Submersible powerheads and wave-making pumps also add to the heat load in the water. All electric motors generate heat. If they are submerged in the aquarium, they will help to increase the water temperature. Back in the early days of reef keeping, we used metal halide lighting. The thought process went something like this.  The sun is a huge bright burning mass of gas. Reefs are lit by the sun. We need the sun over our aquariums to keep corals alive. We then proceeded to hang metal halide lamps over our reef tanks. This required huge energy-hungry ballasts to power the bulbs. The lights were so bright you could not really look straight at them. The heat released by metal halides was dangerous. Many aquarists experienced the “arm burn” by accidentally touching the bulb or the metal fixtures. It was very difficult to keep aquariums cool when lit by metal halides. Even fluorescent lighting produces substantial heat and raises water temperature.

How to Keep Your Reef Aquarium Cool

It has never been easier to reduce heat loading in your reef aquarium. This is good news on several fronts. Unlike in the past, we now know we don’t need the power of ten suns blazing in our living rooms and basements. Sure, deeper tanks still use high-powered lamps, but for most of us, we have better options. New LED lighting fixtures run much cooler than halides and even fluorescent lights. While the initial investment in LED lighting may seem a little high, the reduced heating and low energy use will pay for itself in no time. The other benefit to LED technology is longevity of the “bulbs” and the fixture itself. Unlike metal halides and fluorescent tubes, light-emitting diodes last for years, saving money over time. Heat also causes the plastic to become brittle and weak. I once worked in a lab that maintained twelve 90-gallon reef aquariums. The lighting was a combination of metal halides and florescent tubes, in a plastic and metal housing. Within a year the plastic began to crack, switches broke and fans failed due to the excessive heat. Speaking of fans, LED fixtures do not need big noisy fans to cause distraction in your aquarium room. Obviously, my first choice of lighting is LED. If you decide to go with florescent, carefully choose how much lighting your reef will actually need. Buying bigger, when unnecessary, just adds cost, heat and electrical usage.

We all know water flow really helps the corals and rock stay healthy and clean.  Just like lighting, use just enough pumps and wavemakers to get the job done. There is a new and exciting wave-making technology available that places the electric motor on the outside of the aquarium, magnetically coupling the pump impeller through the glass. This keeps the motor out of the water so heat transfer is all but eliminated. Yes, it is expensive but if you have heat problems, this system will definitely help.

For some reef aquariums the only way to keep the water temperature safe is with a chiller. Chillers work on the same principle as air conditioners and refrigerators, but extract heat from water instead of air. Today’s chillers are compact, efficient and quiet. If you aquarium simply won’t cool down, a chiller is a way to go. Consult your local fish shop for sizing information.

 What about an Aquarium Heater?

Even though most reef keepers are all about lowering the water temperature, there can be times when heating is necessary. In cooler climates and winter seasons the water temperature in the aquarium can become too cool, even in a heated room. A properly sized heater will safeguard the tank from cool periods and stabilize the temperature. Some chillers have a feature that controls your aquarium heater in case the water temperature gets too cold.

 Keep a Cool Head!

Fortunately there are many ways of keeping your reef temperature in the ideal range. If you are still using old school lighting it may be time to invest in LED technology and begin saving money. If you’re running a lot of pumps, try cutting back and see if the temperature drops. Go through your system, piece by piece and find what is causing the heating issue. Then consider which of these solutions will solve your problem and get your reef temperature under control.







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