Aquarium pumps are used to import and distribute air in the aquarium normally through air stones or an air powered filter.
An aquarium pump is not an essential for your aquarium unless it is needed to make another bit of equipment work, such as a protein skimmer or a filter. Fish can survive with the air that is already in the tank.
Other than to power a filter or protein skimmer there are several reasons to install am aquarium pump;
Some aquarium filters are powered by air pumps, these include box filter, under gravel filter and foam filters. Foam filter are a good choice when raising fry (baby fish), as there is less chance of the fry getting sucked into the filter and killed than with normal mains powered filters. Foam filter are also used when keeping Siamese fighting fish, as these delicate fish sometimes get themselves stuck to the inlet pipe of more powerful filters
There are a few things you will need to think about before choosing which air pump to buy, these include;
How much noise can you tolerate? Air pumps work by vibrating a rubber diaphragm which then sucks air into the pump. The vibrations from the pump can be loud depending on the model used. Technology is always improving and many air pump manufactures claim that their pumps are near enough silent. The bigger the pump the more noise it is likely to create.
What is the size and depth of your aquarium? The size and perhaps more importantly the depth of tank dictates what size pump you need. The depth is important because the deeper the tank is the further the air pump has to pump the air and therefore the harder it has to work.
How many attachments are you planning to power? If you are planning to operate one small air stone you will only need to buy a small pump. If you are planning on powering many different air pump accessories you should consider getting a pump with two outlets instead of one. The extra outlet will give you much more flexibility when installing the pump and accessories.
When setting up you air pump there are two essential accessories you must also buy;
Why you need an airline is pretty straightforward; to carry the air from the pump into the aquarium. Why you need to buy a non return valve is less obvious. The non return valve stops water from the tank escaping down the airline into the pump. This is not a problem when the pump is switched on and pumping air. It is when you turn the electrics off (or example to clean the tank) that the water will start to siphon itself out of the tank. Non return values only cost a few pounds and are very easy to fit.
I would also suggest buying some lead weight, the sort you use to weigh aquarium plants down or alternately some suction cups. You can buy suction cups designed to be fitted to airline and they are pretty cheap. I suggest these two items because air stones don’t like staying on the bottom of the aquarium where they belong. The pressure of the air escaping from the stones forces them up to the surface of the aquarium, which kind of defeats the point of having air stones.