Types of Aquarium Power Filters with Advantages

In the early days of fish keeping the choices of filters to use were basically one design, the under gravel filter (commonly referred to as a UGF). This was basically a plastic plate with holes in that sat under the substrate in the tank. It worked by air being driven into it by means of piping which created a water flow through the gravel, cleansing the water as it travelled.

Those days have long gone; there is now a wide variety of powered filters on the market that gives us much more scope to choose which system we wish to use.

There are basically 2 types of powered filter, an internal version, or an external one. So how do we know which one to use?

A lot of the decision involves the tank size that we have, but in some set ups it can also be influenced by stocking load or even if we want to create extra current for various biotopes.

The general rule is that for the smaller set ups an internal filter is sufficient for the tanks needs, as we progress to larger tanks then we should be considering upgrading to an external filter system. In fact the 100 gallon tank that I am running at the moment has 2 externals connected to it ,this gives me much better water quality plus I then have the option of adding a lot more choice of filtration media.

Internal Filters

Internal filters are fine for tanks up to 3 foot in length, after that I would definitely use an external filter. Internals are composed of a small housing chamber for adding sponges to; water is then drawn through the sponges by means of an electric impellor, the water is then passed out from the filter through a spout or with the addition of a small spray bar to slow down the speed of the current. They are attached to the tank with a bracket that will have suckers attached. This means that they can be placed anywhere in the tank, and at any depth. Most of the better internal filters will have an opening on the top for allowing air to be drawn in with the water; this will keep the tank well oxygenated.

Some models will have a lever on them to control the rate at which the filter will take in the water; this is useful if your tank inhabitants prefer more peaceful water flow. These can also be used alongside external filters if you wish to remove any dead spots in your tank, correct placement of the internal will add current that the externals cannot reach. Disadvantages of using internal filters are that they can only perform mechanical and biological filtration in most cases as inside the housing there is only room for the sponges, no other media.

All of these filters will have a rating on them for the correct tank size to use them in, Fluval for example, have brought out the plus series (plus1, plus2, plus3, plus4), which means that looking at the model number you will get a good idea of which one you require.

Take for example the plus 1 model, this is rated for tanks holding 12 – 15 U.K. gallons of water, it has a flow rate of 50 U.K. gallons per hour.

As you move up to the plus 4 the tank size it can handle increases to 60 U.K. gallons of water, the flow rate increases to 260 U.K. gallons per hour.

Bear in mind that the smaller internals normally only hold one filter sponge, whereas the larger ones will take two.

External filters

These are the most advanced of the power filters. They comprise of a main chamber which will hold a number of trays or baskets that will contain the chosen media that is required for your system.

Water is piped into the chamber by means of an impellor. The intake is placed inside the tank and a length of tubing is then joined to it to create a connection to the main chamber. The same applies to the outlet, this has a length of tubing which is fixed back to the tank where a choice of connections can be added to allow the water to re-enter the tank after filtration. The connectors supplied are normally a spout and a spray bar. The spout is used if direct water flow back into the tank is required, however if the current needs to be slow and gentle, then the spray bar should be attached. Basically this is a length of rigid tube with holes in it from one end to the other. As the water is passing through the holes, the return flow has no choice but to be slowed down.

I prefer the spray bar method, in all of my set ups it is placed level with the water surface so that ripples are formed to keep any oily film forming on the surface.

The media placed inside the filter is purely a matter of choice depending on which fish you are keeping. Sponges are a must for the mechanical filtration. Ceramic rings make a great host for the bacteria required for the biological filtration, as for the chemical I normally add phosphate and nitrate remover.

As with the internals most suppliers will do a range of different rated models depending on how much water you have in your tank.

A quick is example is the basic Ehiem range. The smallest external in this range is capable of a water flow of 390 l/h whereas the largest version is capable of a water flow of 790 l/h.

The Eheim professional range can also include built in heaters and UV sterilizers.

Basic Maintenance & Tips

When selecting your filter, remember after a period of time that the flow rate will decrease as the media starts to get clogged.

Take your time with the placement of filters; dead spots in your tank are excellent places for your nitrates to increase.

A good investment is a set of cleaning brushes for your filters. Every month or so your filter will need a good clean out. This includes rinsing the filter media in old tank water, checking the tubing for blockages, and another job often missed is giving the impellor as good clean with a brush. This is not a complicated job as the impellor covers should either screw off or just click off, then it is just a case of sliding the impellor out carefully, making sure that the shaft does not get broken.

To replace the impellor, simply slide it back in, making sure that it has been inserted the right way.

There are many filters to choose from ,making your decision on which one to buy can be made a lot easier by researching first, some of the filters are not cheap items, it is best to make sure whichever one you do decide to buy will be right for what you need.