Saltwater aquarium fish

The stability of the water temperature is very important for a marine tank. Marine fish survive in a very stable temperature environment. This is because the seas have such a huge mass and changes only occur slowly, especially in tropical locations. There is also the impact of global warming or cooling. Salt water tropical fish in an aquarium can withstand temperature changes, provided they happen slowly and if the temperature rises or falls, by only a few °C. You don’t have to be scared if the temperature falls a bit during some occasions.

In almost every country you will need a heater for your tropical salt water aquarium, as there are few countries in which the winter is hot enough so that you will not need any form of heater. On the other hand, you will not need any aquarium heater if you want to own a tank with fishes from cold water seas.



There are a number of options for heating your tank. The most common is a normal heater which looks like a stick and is fully immersed into the water. The problem with this kind of heater is that it has to be totally isolated from the salt water. If water finds it’s way into the heater, it will corrode and can be discarded. (please be sure to recycle it). Salt water will rust and destroy everything which is not fully protected, including all forms of steel and even rubber. Only plastic and glass are suitable for use in your salt water tank. The best method to determine suitability is to read the instructions given by the manufacturer. Only heaters that are specified as suitable for salt water aquariums, should be used. If anything goes wrong, at least you can say that it is within the product’s guidelines that it can be used in salt water. You should be able to claim a refund if it is then damaged by the salt. You may use a freshwater heater provided you cover the metal parts with plastic. This is risky, because you may not cover the heater correctly and the water may seep in and damage it. In extreme cases it can result in electric shocks. This will prove fatal to your fish and if you put you hands into the tank, to see what is happening, or to take out the dead fish, it may kill you too! If it is used as it should be used, it is my favourite type of heating the tank, because it has a thermometer and you can choose on which temperature you want to have the water heated. If the temperature is higher, the heater will shut down, it will save money for electricity, and the best of all, it will keep the temperature stable. Another advantage is, that there is no heat loss, because the heater heats just the water. Because it is simple, inexpensive and effective, it is the most commonly used heater both in fresh and salt water tanks.

On the market you may find many types of these tank heaters. They have different wattage, so which one should you choose? It depends on how large your tank is. Some say that if you have a 90 litre aquarium then you need almost 1.7W per litre, so you will need about 150 watts. For about a 200 litre tank, you need approx 1W per litre and for greater volume, you need less than 1W. It does depends on how fast you want to increase the temperature and also on the temperature of the room (if the room temperature is 15°C then you need more powerful heater than you would if the temperature was higher than 20°C) Eg. If you set up the tank and it is already about 20°C, you will not need a very strong heater. In this case for a 90 litre big aquarium you may need only one 50W small heater. For bigger tanks you may also use two small heaters. If your aquarium demands 100W, you may use two 50W heaters and situate them to opposite sides of the tank. If you heat the tank this way, the water will be heated in a consistant manner, with no significant variation.

If you are using this type of heating for your marine tank, you should be careful when you are changing large volumes of the water. If you empty out the water and the heater is still on, the heater will continue heating because it wants to heat up the whole tank. Then when you put in cold water and it makes contact with the heater, there is a big chance that it will shatter. You must be sure to turn off the aquarium heater every time you are changing the water. Please do not touch the heater as you may get burnt! Make sure that the heater is not in contact with the gravel. It may overheat the gravel and fish and creatures which live in or on the gravel, may get burnt.

You may choose to use an under-gravel heater. It is also effective and there are no losses of heat, however it is not usually practical. If something goes wrong and the heater ceases to work, you have no choice but to remove all rocks and gravel, to replace the heater. This can be very stressful for the fishes, because you have to remove all the decoration, caves, rocks and plants too. There can also be problems if you are using under-gravel filtration system with under-gravel heating. It is also vital to ensure that these heaters are salt water resistant.

Occasionally you may find some heater pads. This type of aquarium heater is very specific. It comes under the tank and heats it from the bottom. It looks like an electric blanket which you may use at home, you just place it under the aquarium. There are no problems regarding the fact that the heater is waterproof or not, and the salt water will not destroy the equipment. However, if the aquarium springs a leak, it will be lost. Needless to say, the last thing on your mind will be the loss of your heater if such a situation occurs. As always, there are some disadvantages. This type of heating is not the most effective, because it will heat the glass, the stand but also the air, not only the water. Another problem is that if the pad brakes down, you have to lift up the whole tank if you want to repair it, or change the pad.

At last I am going to write something about the method of heating which is based upon the temperature of the room. You heat up a room where the tanks are and the hot air will heat the tanks too. This method has it’s advantages and disadvantages. Advantages include that you can heat the tank without using any heater immersed into the water, so you don’t risk the break down caused by salt water. Also it is possible to heat up more tanks, not only one, and this method is the best for heating more than one tank. It is used mostly by breeders, who have a whole room full of salt water, or freshwater fish. The disadvantages are that you lose a lot of energy while heating up the whole room and the electricity is not cheap. You must choose a small room, maybe without windows. You can see that in such case the tanks could not be in the middle of the living room where you can watch and enjoy them all day. The room has to have a high temperature and it is not very comfortable to work in, nor enjoyable to watch the fish, due to the high temperature and humidity.

The best way is to control the heating by an accurate thermometer. You can choose from thermometers which may be stuck to the glass, or those which are placed in the water. External thermometers may not show the right temperature because they are influenced by the temperature of the room. Internal thermometers may break in the tank, so you should by a thermometer which has a safe filling, like alcohol thermometers. If you have a deep marine tank you should have two thermometers. One near the surface on one side of the aquarium and another near the bottom on the opposite side. This is because of thermal layers in the water. You may experience problems when the circulation of the water is insufficient and the temperature is different at the top, than it is at the bottom. Also the thermometer shows if the water is heated normally. If the salt water aquarium heater is not working correctly, it may damage the thermometer, so you should pay close attention when working on the tank.

When we are speaking about heating of a salt water tank, I should mention the insulation of the aquarium. A good insulation reduces costs. I recommend that you use polystyrene on the back and on the sides of the aquarium. Naturally this should be on the exterior of the glass. Do not put the polystyrene into the water. Leave only the front glass free, so that you can see what is happening in the tank. You may add an aquarium background on the polystyrene, so the tank will look like it is in the open sea and that is has no end. You should not keep the marine aquarium open as well. The hot air will rise and heat loss will result. Aquarium hoods act as an insulation and may have some openings for the aerator. This also allows fresh air to be absorbed into the tank. The best insulation is to have the largest aquarium you can, as the more water you have, the slower will the water cool down. If there is an electricity blackout, the greater the volume of water, the longer the temperature is stable.edit this page or create a new one