If you keep tropical fish then heating the tanks will be your biggest expense. Most tropical fish come from much warmer places than the UK and usually come from large rivers or lakes so the temperature is kept quite stable. This is very important if we want to keep our fish healthy and happy. Sudden changes of temperature by even just a couple of degrees can seriously stress your fish. Stressed fish are much more likely to suffer from an illness as their immune system will be weakened.

If you are lucky enough to have a fish room or fish house, which is basically a collection of tanks in a dedicated spare room/garage/or shed, then please read: Heating a Fish Room.

If you just have the one tank in your house then heating wont be too much of an issue. These days most houses are centrally heated so a simple heater thermostat from an aquatic shop will do the job just fine. However there are still things you can do to reduce your heating costs especially if you own a large tank or several tanks around your home. These tips are listed below.

• Place your tank in the warmest room. Most people like to have an aquarium in the main living room. This is usually ideal as it is often the warmest room as people spend most of their free time there. Plus you probably want your tank to be seen and admired! I would not recommend placing your tank in a unoccupied room like a spare bedroom. As the heating may be turned down in these rooms and it would be harder to spot any problems if your not in the room very often. I would also be careful about placing a tank in the kitchen. Kitchens often have big fluctuations in temperature. It can get very hot when cooking in there but it can also get quite cold as a lot of kitchens don’t have radiators and often have a back door.
• Don’t place tanks in front of a radiator or window. Just as we don’t want our tanks to get too cold we also don’t want them too hot. Radiators and direct sunlight can heat water very quickly! Sunlight can also cause other problems like algae or green water.
• Get the right heater. The basic rule is 1 watt of heat to 1 liter of water. It is fine to have more than this but don’t go lower. I would always recommend having two heaters per tank, placed at either end. Heaters can and do fail so it is always best to have a back up. If you have a 300l tank then two 150w heaters would be fine. Having two heaters should also heat the water quicker which means they are on for less time which saves you money. Ideally you want the two heaters set to exactly the same temperature. Although different heaters may not be perfectly calibrated so keep an eye on them to see if they both click on at the same time. You can then slightly adjust one if you need to.
• Make sure you have enough circulation. You need to have water moving around the tank to distribute the heat evenly. Most internal or external filters will do this job adequately although correct placement of the inlets and outlet pipes can help. This is another reason to have two heaters especially in a long tank. Also make sure the heaters are placed fairly low in the tank, as warm water rises, and place them at an angle not vertically or horizontally.
• Always use a tight-fitting lid or cover. Most heat loss in an aquarium is through evaporation. So this is very important. It also reduces the amount of water lost in the air which means you won’t need to keep topping your tank up.
• Insulate! If you are keen to save money and reduce your carbon footprint then you need to insulate. If your house is not properly insulated then forget about your fish tanks and get it done as soon as you can afford it. You will save a fortune off your energy bills if your roof and loft space is properly insulated. Cavity wall insulation also helps a great deal. During the winter months you can also insulate your fish tanks. Just simply cut some insulation boards or polystyrene to size and fix it to the back and sides of your tank. If you don’t have a background picture in your tank then I would paint the insulation as white polystyrene can startle your fish and make them nervous. I usually paint mine dark blue but black is fine. If you are artistic you could paint an interesting background with trees, rocks, or anything you like. If painting, be careful not to get any near the water as most paints are toxic. Use silicone, blue tack, or sellotape to fix the boards as you will need to remove them when winter has passed.
• Use reflectors in your light units. If you use strip lights, usually T8′s or T5′s, to light your tanks then make sure they have reflectors. They are silver and curve behind the bulbs to help reflect the light down into the tank. Not only will they maximize the amount of light going into your tank but they also reduce heat loss. You can buy reflectors to fit most bulbs or you can make your own with tin foil. My 6 foot tank in my living room doesn’t have a lid, just a sheet of cover glass. So I got a long piece of roof guttering, cut it to size, fitted end caps, and glued tin foil (cooking foil) to the inside. Then I fitted two plastic clips to hold the light bulb in place as you don’t want the bulb to be touching the foil. It worked great, however I have since upgraded to LED lighting as they are much more energy efficient. You don’t need to use reflectors with LED’s as they create focused points of light. They don’t generate much heat either.
• Use an old quilt. Even in the coldest days of winter it is often too expensive to run your central heating 24 hours a day. I run mine for several hours in the evening then switch it off when I go to bed. I then set it to come on an hour before I get up in the morning. The temperature can drop quite significantly during the night so after switching off my tank lights before bed I throw an old quilt over the whole tank to keep it warm. Always remember to take it off in the morning and make sure that the lights are off and that the quilt does not cover any air pumps or other electrical items as they can overheat. I would also recommend that the room is darkened before removing the quilt so as not to startle your fish.