Choosing the right filter is one of the most important steps in setting up an aquarium, but with all the factors that you should keep in mind and the many different filter types and brands available, things can get slightly confusing.
To hopefully clarify things a little, keep reading for a list of the most common filter types and their pros and cons!
Probably the most common filter type is the internal filter. These come in most aquarium kits or you can buy them separately at pretty much any pet- or aquarium store and online. Internal filters are usually pretty cheap, but the quality unfortunately varies and they do take up a lot of precious space in the aquarium. Some of these filters can produce a rather loud whirring noise, which really isn’t ideal, especially if your aquarium is set up in a bedroom.
Most internal filters also only contain sponge and miss the important biological filter media that contains most of the beneficial bacteria and helps keep your cycle stable. That all being said, internal filters should usually work fine, especially for smaller aquarium setups. If you get one that is high quality, they are a nice and cheap option. Just be sure you buy the right type for your aquarium size. Cut off part of the sponge and replace it with biological filter media such as bio balls and you are all set. You can also hide the filter, as pictured to the right.
A popular internal filter is the Aqueon QuietFlow.
Though not very popular for nano aquarium setups, a canister filter is usually actually the best filter choice you can make. They can get a bit pricey and are sometimes a bit difficult to set up for beginners, but they have many advantages. They don’t take up space inside the aquarium, as they are actually meant to be placed underneath it.
Canisters are also great because, unlike many other filter types, they have plenty of room to layer filter floss, sponge and biological filter media effectively.
If you have a larger aquarium or keep fish that produce a lot of waste, looking into buying a canister filter is a good idea. My favorite is the EHEIM Classic and although these filters are obviously a bit more expensive, they are very high quality, come with different options for filter media and intake/outflow and will last for years. Replacement parts of the more popular brands usually easy to find as well.
Hang on back filter
Hang on back (usually abbreviated to HOB) filters do exacly what the name suggest: they are supposed to be hung on the back wall of your aquarium. These filters can work quite well for smaller aquariums, especially due to the gentle “waterfall” flow, but they do have some disadvantages.
HOBs aren’t ideal for larger or more heavily stocked aquariums, as their power and room for filter media is often limited. Biological filter media is not included in many cases. Another, more practical disadvantage is the fact that these filters sit on the back of your aquarium and therefore aren’t always easy to accomodate! You may need to remove part of your aquarium hood and it’s not possible to put your aquarium against a wall.
Like internal filters, hang on back filters are not the absolute best choice. However, they work great for smaller or more lightly stocked aquariums. Just be sure to find one that has room for biological filter media and not just sponge, such as the AquaClear. This filter, like many others, does come with an activated carbon pad which you should ideally take out and replace with more biological filter media. These pads are really only necessary for emergencies.
Sponge filters are different from the other filters mentioned because they are not powered by an impeller. Instead, they are powered with air. Because the water flow is usually quite weak and most sponge filters don’t contain biological filter material, they are not suitable for most setups.
As mentioned in the intro of this article, sponge filters are ideal for temporary hospital tanks and small, lightly stocked aquariums around 5 gallons (18L) like as shrimp tanks and snail breeding tanks. Frail fins and tiny shrimplets can’t get sucked into the filter and the outflow will never be too strong.
Sponge filters are hooked up to an air pump, which creates the water flow (and a pretty bubble effect). Most are nothing more than a piece of sponge and thus very cheap, although you do have to keep in mind the cost of a separate air pump and tubing. If you’re interested in using a sponge filter, keep in mind that all air pumps create noise and some are very loud. If you want to use more sponge filters at the same time, getting a stronger air pump such as this one with a multi-way valve is a good idea.
If you’re looking for a filtration system for a big aquarium or even an indoor pond and don’t want to buy a very expensive large canister filter (or just want a super effective filter with loads of space for biological filter media), a pond filter or a trickle filter is probably the way to go.
A trickle filter or wet/dry filter is a large filtration system that is placed underneath your aquarium. Water flows out of the tank into the trickle filter, where it trickles through biological (and sometimes mechanical) filter media into a sump (water holding space) and back into the aquarium using a pump. This “trickling” process exposes the water to lots of air, which is beneficial for the bacteria growing in the filter media.
A trickle filter is a very effective filtration system that can be used for very big aquariums with messy fish, but also for “regular” aquariums under 100 gallons (380L). Trickle filters are mostly used by more experienced aquarists because making a DIY one can be quite difficult and buying one (especially for bigger setups) can get a bit expensive. However, theres no reason you shouldn’t use them yourself, as they are very effective! An example of a trickle filter for smaller aquariums is the Eshopps wet/dry filter.
It’s not a very popular option for aquariums but if you can handle a bit of noise, a pond filter may be an option for you. There is a lot of of room for biological filter media (such as lava rock) and the filter is very powerful. It does create a very strong flow, so I wouldn’t recommend a pond filter for regular setups.
Another thing to keep in mind is that some pond filters are supposed to be placed above water level, so you may need a way to raise yours. An example of a pond filter is the Pond Boss filter kit.
- For more information on biological and mechanical filter media and what they do, check out how aquarium filters work.
- For more information on why the beneficial bacteria in your filter are necessary for a healthy aquarium, check out how to cycle an aquarium.
If you have any more questions about choosing a filter or if you want to share some additional knowledge, don’t hesitate to leave a comment below!