The Heater

As we discussed earlier, water temperature is one of the most important concerns of fishkeeping. Too warm or too cold could cause your fish to be sluggish, or it could kill them. Fish are sometimes grouped into categories based on their temperature preference. However, as far as the beginner aquarist is concerned, most freshwater tropical fish that he or she is going to see at their local pet emporium will probably require a similar temperature. Most of these are of the tropical species.

Tropical fish live in habitats where the waters are warm throughout the year. They don't know where you live and don't care. They need the water at their temperature—there really is no compromise. And thus was born the aquarium heater.

Regardless of the room temperature, the aquarium heater will maintain your fish tank temperature at appropriate levels. It is only natural that these temperatures fluctuate as the heaters react to changing temperatures outside of the tank, so it is important to note that you should be looking at a range. You don't have to keep the tank at one immovable temperature. This would be impossible. You should consult your local pet dealer or one of the many fish encyclopedias for specific temperature requirements.

The submersible glass tubular heater with a built-in thermostat is the most common of all the different kinds of heaters available to the aquarist. It has external controls so that it can be adjusted, and clips onto the side of the tank, with the glass tube submersed in the water. Generally speaking, the heater will automatically adjust to temperature changes once it has been set. Some manufacturers have preset temperature dials, which makes it that much easier for the beginning hobbyist to use.


Almost all heaters come with automatic thermostats. These work very much like the ones in your own home. They will help you set a fairly consistent temperature range that will be comfortable for the fish in your tank. However, you need to remember to be careful that no outside forces, such as radiators or sunlight, will be able to heat the tank up too much. Heaters can warm the water, but they cannot cool it.

Regardless, the temperature gauge is easily set by the user. It is important to note that the use of a thermometer is the only good way to constantly monitor the heater's functionality and accuracy. We strongly urge you to always check a thermometer to measure your heater's success.

Sleeping with the Fishes

Shhhhh! Your fish is sleeping. You can tell when a fish is sleeping because it usually lies on or near the bottom, sometimes hidden behind plants. It moves just slightly, but it does not swim.

Do tropical fish close their eyes? No. They can't. Their eyelids are clear. So when they are asleep they may still look awake. It's also important to remember that in nature, fish usually sleep when it's dark. Sleep is just as important for tropical fish as it is for human beings. It helps them rejuvenate and remain healthy and vibrant. So let them sleep at night. And remember to turn out the light!

We have often found that one of the best areas to place your heater is near the filtering system or an airstone. The idea is to place the heater in an area of high water circulation, so that the heat can be evenly distributed throughout the tank. Some heaters are fully submersible. Generally, these are placed at the bottom of the tank, and allow for maximum penetration of heat. However, they are more expensive, and not always as reliable or as easily replaced as the submersible glass tubular heater.

Again, with heaters, size matters. The size of your aquarium dictates the size of your heater. The general rule of thumb is five watts of power for every gallon of water. Thus, a 20-gallon tank would require a 100-watt heater. A 30-gallon tank would require a 150-watt heater. If you have a tank of more than 50 gallons of water, you will need two heaters. It's not as important to be able to just heat the water as it is to heat it evenly. Especially if one heater fails, then you are covered. In such cases, you would want to evenly distribute the wattage. A 40-gallon tank would require two 100-watt heaters, placed at different spots in the tank.

The Thermometer

Here is one absolute rule: All aquarists need a reliable thermometer! We don't care how good your heater is, or how good your sense of approximating it yourself might be. In order to maintain your temperature at suitable levels, all aquarists need an accurate thermometer.

There are two kinds of thermometers: the external stick-on kind and the internal floating or fixed kind. The internal type tends to be more accurate since the external type has a tendency to read a couple of degrees too low.


While it does not cost a lot of money, certainly the thermometer is one of the aquarist's most valuable tools. We recommend two thermometers. This will allow you to carefully monitor your aquarium temperature by letting you compare their reports as well as gauge them one against the other. When it comes to maintaining water quality and water temperature, don't be lazy or cheap. Buy these and it will stand you in good stead.


Unless you want hair like the Bride of Frankenstein or really enjoy hospitals, we strongly suggest that you handle all electrical equipment with extreme care. The heaters are the most dangerous electrical components in your tank. As with all electrical devices, please handle your heater with extreme care. Do not switch your submersible heater on until it is submersed in water. Keep all of your electrical components unplugged until the tank is completely set up and full. Heaters turned on before they are submerged may burn out or at worst explode. Also, you don't want to be handling live wires with wet hands.

Full Spectrum Lights

Incandescent and fluorescent lights do not provide the full colors in the spectrum like natural light. Today many lights, which come close to recreating sunlight, are available on the market. These light bulbs are excellent, especially if you have live plants. Ask your pet store professional which ones he or she carries and ask for a recommendation from their selection.

The Light

Good lighting makes for a good tank. It promotes plant growth, which is very good if you have plants. But more important, it provides you and your fish with illumination so that they can see their way around and you can see them. Yes, the sun could easily provide you with plenty of natural, cheap light. But don't put your fish tank in front of a window. If you do, you'll be scraping algae off the insides of the tank for more days than you'll be able to see the fish. And they said nobody does windows anymore!

We recommend that the beginner buy a commercially manufactured light for the tank. Like many of the other items we've already talked about, these come in a variety of shapes and sizes. If they are not part of the hood, they should fit snugly on top of the hood. The one that most aquarists buy are fluorescent lights, because they don't heat the water, and they provide light evenly.

The interesting thing about fluorescent lights is that they come in a variety of colors. These can be used to create special effects in your aquascape. There are red and blue bulbs that will enhance the reds and blues on your fish while also promoting plant growth. There are fluorescent bulbs that also cover the ideal spectral range that will ensure good plant growth. These bulbs are not uncommon and can be found at any well-stocked pet shop.

If you bought a hood with a light as we suggested earlier, then that was almost certainly fluorescent as well. If you do not purchase a tank, cover, and light package, make sure that the light that you buy extends the entire length of the tank. This is by far the most efficient and economical form of lighting available for your tank, and we thoroughly recommend it for the beginning aquarist.

Tank Bulbs

Rock-A-Bye, and Good Night

Just like us, fish need to get their beauty rest! In the real world, the fish live by the same daylight hours we do. During the long summer days they are active until late in the evening. However, in the winter they go to bed early. What do they do in the dark? They sleep!

Make sure to turn off the light at night. Fish need to sleep, and will rest on the bottom hidden in plants, or behind rocks. Without a proper amount of time for rest, they will tend to be less healthy and less active. So if you want healthy fish, give ‘em a break!

Are there other types of lights? What are they? Well, there are many other types. These include incandescent, sodium, mercury vapor, metal halide, and tungsten lights. They provide unique lighting opportunities, but tend to heat the water and are not as economical as fluorescent lights. We do not recommend any of these.

There are several things to consider when you buy a light for your aquarium. Make sure that you take into consideration the depth of the tank, the number and kind of fish you intend to have, and the number and kind of plants you intend to place around the aquascape.

If you don't have enough watts, it will be difficult to see some of your fish, and you won't be supplying enough light for your plants to grow. We generally go by a ratio of 2 to 2.5 watts per each gallon of water. More plants and fish might necessitate the need for more watts.

Again, consulting your pet professional with the specifics will help you come to a good decision. Consult them before you buy your setup.


Most tropical freshwater fish come from regions where daylight lasts from 10 to 15 hours a day. That's a long time. To make sure you're giving your fish enough light, you need to make sure you leave the light on for those same hours so that they can be healthy and at their best. To ensure proper light hours for your fish, consider buying an automatic timer. That way you can set the timer so that your fish will get their 10 to 15 hours a day, and you won't always have to run over and remember to turn off the light.

An average of a 12-hour day is recommended by many experts. Another trick to keep from startling your fish is to turn off their light an hour before the rest of the lights are shut off around the house. This provides a simulation of sunset for the fish, so that they won't be startled when it's time for lights out.

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