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Things to know about aquarium heaters - FAQ

Resized image of aquarium heater, 1 Resized image of aquarium heater, 2 Resized image of aquarium heater, 3

Brief Description

This article is a collection of answered questions that fish keepers ask the most in regards of heaters and heating fish tanks. You're welcome to ask questions in case you can't find answer on your question below; Also visit our most popular article about heaters: A guide on using Fish Tank Heaters with FAQ, Forum and Online suppliers.

One of the most vital pieces of equipment in an aquarium has to be the heater. This is often neglected and forgotten about when placed in the tank but it plays a vital role in the fish’s welfare. Misplacing a heater in the aquarium can often mean cold spots in the tank or the heater cannot run as efficiently as it should be doing, hopefully this article will help give everyone a good understanding of how a heart should be used.

When should a heater be placed in a tank and why are there some tanks without them?

Many species of fish are classed as coldwater fish. When keeping a coldwater tank, there is no need to add an aquarium heater as the fish prefer to live in cooler temperatures. Sub tropical and tropical fish come from climates that have higher water temperatures, this is the reason that these fish need to be kept at temperatures above room temperature.

How does a fish tank heater work?

The heaters that are used for aquariums are basically an element enclosed in glass or stainless steel and the temperature is controlled by a thermostat. With every heater there will be an adjustable dial that you set to obtain the required temperature for your tank.

How much do aquarium heaters cost?

There are many brands of aquarium heaters available; they vary in price according to the quality and accuracy of the heater. A basic 50 watt heater will cost about 9 pounds (18 dollars), a titanium heater that is very accurate can cost up to 40 pounds (80 dollars). The golden rule is to always buy the best heater that you can afford; it will pay dividends in the end.

Which brands of aquarium heaters are considered to be the most reliable?

There are many brands of heaters to choose from, the brand you use is often down to personal choice, one person may use one brand all of the time, another person may think that another brand is a lot better. The most popular aquarium heaters that are generally seen on the market are made by companies like Tetra, Azoo, Marineland, Hagen, Rena, Fluval, Tetra, and Eheim. There are more but too many to list.

In the UK it seems to be the Fluval, Eheim, and Tetra that are mostly used but nowadays there a lot of imported Chinese makes coming onto the scene.

What is the correct way to install an aquarium heater and are they fully submersible?

The correct way to install a heater is to place it at the rear of the tank in the water flow from a filter. This will enable the heat transfer to be constant all over the tank. Cold spots need to be avoided at all costs. Never lay your heater down on the substrate, using the suckers or brackets that come with the heater, attach it to the back of the tank at a 45 degree angle. If the heater is simply laid down on the substrate, most of the heat emitted will be soaked up at the bottom of the tank and not into the rest of the water. Nearly all available heaters are fully submersible but always double check before you place them in the tank so that there can be no doubts.

I am currently using a titanium heater with a separate thermostat, the heater element can be submersed but the thermostat has to be kept away from the water and is fixed in a separate location.

How long should I leave the heater switched on every day?

Once the heater is installed, leave it plugged in all of the time. As it is thermostatically controlled, it will turn itself on and off as required. The only exception to this rule is when you are performing a water change and the water level is going to drop below the safety level marked on the glass exterior of your heater. In this case, unplug your heater before starting the water change but don’t forget to plug it back in once you have finished.

How do you know if the aquarium heater is on?

With every heater system, there will be an LED light on display that will light up when the heater is actually heating the water. When the water is warm enough, the heater will turn off and the light will go out.

How do I know which size heater to get for my tank?

The size of the heater required for the tank is determined by the amount of water volume the tank holds. With the packaging of every heater there will be a chart guide that tells you which size heater you need for which size tank. It goes without saying that the larger the tank the larger the heater required.

The general rule is that 5 watts of heater is required for every gallon of water in the tank. This means that if your tank is 5 gallons, then a 25 watt heater will be needed, for a 50 gallon tank a 250 watt heater is needed. Remember that the larger heaters go up in stages of 100 watt intervals so if 250 watts is required, you will need to purchase a 300 watt heater.

What do I do if my tank water volume is too large for one heater to cope with?

The easy solution to this is to place two heaters into the tank, one at each end. If your tank is 300 gallons you will need 1500 watts of heating. In this case you will need to add three 500 watt heaters so that the correct temperature can be reached.

Does room temperature affect the temperature readings?

If your tank is situated in a cooler room, then you should add a larger heater to your tank, in a warmer room, the heater will be doing less work. A tank without a heater will also be affected by room temperatures; remember this when keeping coldwater fish.

Can I use a 200 watt heater in a small tank?

Theoretically you can use a larger heater in smaller tanks, the only downside to this is the fact that the water may over heat and affect your fish. It is much better to use the recommended size for the tank you have.

Do I need a heater in a planted tank?

Most plant species do better in a heated tank but some are perfectly o.k. in a coldwater set up. For coldwater use plants that are proven in ponds as you know they will survive. Most good plant dealers will let you know which temperature the plants prefer.

How do I know what the temperature of my tank is?

The only way of answering this is to tell you that with any heated tank you must add a thermometer to the tank so that you can check on a daily basis how warm the water is. Thermometers are relatively inexpensive but could save you a lot of problems.

Can I keep guppies in a coldwater setup?

The answer to this is yes and no!! If the parents were raised in coldwater then they will be alright, but if they are purchased from a shop that keeps them in warm water then they should be kept in a heated tank at 26 degrees.

How do I heat an outdoor tank?

With the tank being outdoors use a larger heater than you would normally and keep a lid on the tank to prevent too much heat loss. Many ponds are heated and use large titanium heaters, these can be up to 800 watts rating but they do work effectively.

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