Keeping tropical fish is more popular than ever before, and it’s not difficult to see why. Not only is fish keeping a truly absorbing hobby, but further today’s advanced tropical fish equipment means that it’s easier than ever before to keep your fish in top condition. On the other hand, the amount of fish-keeping equipment on the market can make it tough to choose “the best”.
Aquarium filters and fish tank pumps are one of the most complex areas of all, so today we thought we’d examine the pros and cons of the various fish tank filter options.
As the name would suggest, an undergravel filter is placed under the gravel of your fish tank. Imagine a plastic plate, around the size and dimensions of your fish tank. Typically either white or black in colour, these plates are riddled with small holes. Your gravel is placed ontop and keeps the filter plate glued firmly to the bottom of your fishtank.
In one corner of the base plate is a tube, and into this fits an air stone attached to a pump. As the bubbles travel up the tube, so water is drawn down into the gravel. In this way, the water is constantly being cycled around the tank, being drawn through the gravel which acts like a “sieve”, removing particles from the water.
So the next question is obviously what happens to all the muck in the gravel – and here there are two explanations. Firstly, over time a colony of friendly bacteria builds up in the gravel, feeding on the leftover food and faeces. These bacteria slowly digest the biological waste without doing any harm to your fish.
Secondly, depending on the load of bacteria in your tank, you can supplement this natural cleaning ability with a manual clean from time to time. Efficient gravel cleaners are available from most aquarium shops, and make cleaning debris from your aquarium gravel a breeze.
In terms of the pros and cons of undergravel filters, the first point should be obvious. In order to install the system you’ll need to remove all the gravel from your fishtank; not tempting if your aquarium is already set up.
Another weakness of this system is simply how much mess it can create. As the debris is dragged into the gravel – rather than the box of a filter – this can become unsightly quite quickly. Ensuring you have suitable bacteria, and are carrying out manual cleans as necessary, are essential for undergravel filters.
As one final weakness, appreciate that if your gravel is covered – such as by rocks or plants – or you like to keep a very thick layer of gravel at the bottom of your fish tank, the suction power on the water will be impeded.
So what are the upsides of undergravel filters? Well for one they’re probably the cheapest type of filter to install in an aquarium. They also help to aerate the water, thanks to the bubbles being produced by your pump, and once up and running can be very efficient indeed at removing toxins because the entire gravel substrate is being used for this purpose, rather than the much smaller area inside an internal filter.
The next type of filter worth knowing about is the internal filter. These filters resemble a plastic box, and are typically much taller than they are deep or long. They sit inside your fish tank – most commonly in a corner – and filter the water.
In essence these internal filters contain one or more filtration mediums. These may include foam, charcoal beads and/or clay beads. The most effective internal filters use a number of different media, to both remove physical debris from the water and also chemical toxins.
Essentially the pump draws water into the base of the filter, pumps it through the filter material and then spits it out at the top. As the water shoots back out, the surface of the tank is agitated, and so the water becomes oxygenated.
So what are the pros and cons of internal filters? Firstly, of course, having a large plastic box inside your fish tank does a very good job of reducing the actual space available in your tank for fish. In most cases the difference in the number of fish you can keep in an aquarium is minimal, but for some people it may be a deal breaker.
The second factor to consider is that your internal filter will need to have uninterrupted access to your aquarium water. This sounds simple enough; after all, your filter will be sat in the aquarium water. However what you need to appreciate is that plants, rocks and other types of tank décor can get in the way, forcing the motor in the filter to work much harder than necessary. As a result an internal filter may have an effect on your overall tank styling.
Lastly, on the negative side, is simply that some people find internal filters unsightly. They’d rather use a filter that can be hidden from view, allowing an uninterrupted view of your fish.
There are however a number of benefits. Firstly, installing an internal filter is typically simplicity itself. All you need to do is to slide it into the water and use the suction cups to stick it to the wall of your tank. Plug the filter in and you’re up and running.
A second benefit is that internal filters are quite diverse is their design. This means that it is quite easy to change the filter media being used, to custom-make the best filtration for your local type of water.
Lastly, accessing your filter for routine maintenance is of course very simple indeed. Simply lift the lid of your aquarium, reach in and grab the filter. Imagine trying to do that with an undergravel filter and you’ll appreciate the benefit of internal filters in an instant!
The final type of filter worth knowing about is the canister filter. These filters are rather like an internal filter in that they consist of a large plastic box into which the water travels, is filtered, and then exits into the tank.
However canister filters differ in two distinct ways. Firstly, the canister filter is located outside of your aquarium. A small hose system sucks water out of your aquarium, into the canister, and back out into the tank again. The filter is therefore normally stored in a cupboard or suchlike, next to or under the aquarium itself.
The second difference between canister filters and internal filters is that because the filter itself is not actually kept within your fish tank, size is less of an issue. This can have a number of effects. Firstly, a large filter means you can include more filter media, meaning a more thorough clean of your aquarium water. Secondly, as they can process more water, canister filters can be ideal for larger aquariums, where such a large internal filter would be necessary that it would ruin the overall effect of the fish tank.
These are big benefits of canister filters. One final benefit worth mentioning is that as the filter is now located outside the fish tank, routine filter maintenance becomes even easier than before.
There are of course a few downsides, not least the fact that canister filters tend to be far more expensive than either of the other two. In addition, you should appreciate that you’ll need to find somewhere to store the canister safely, and the initial setup – with all the pipes and hosing – can be a little more involved than installing a standard internal filter.