The Aquarium Sump Filter

The sump filter is simplicity in itself and is often constructed using the same materials as fish tanks are made of. You can also use open water tanks that are commercially available, these are often very sturdy and ideal for the purpose.

There are also commercially available sump filters that you can buy but these tend to be very expensive so at the end of the day it may be cheaper to make one yourself. If you don't think you can make one yourself then have a word with an aquarium manufacturer, they could probably manufacture the actual sump for less than £100. Piping and pumps will obviously be an added extra. Most tanks that have a sump installed have had alterations made so that a sump filter can be installed. Adding a sump filter to an aquarium is not like adding a canister filter. Sump filters are normally housed underneath the tank in the cabinet. You would normally have a couple of pipes in between the aquarium and the sump filter. In most cases the actual aquarium has been drilled and pipework installed so water can both leave the aquarium, and be returned. In order to return water to the aquarium you use an aquarium pump. Very large aquariums would require a very powerful pump. Below are some photos of the sump filter I have installed on my 300 gallon aquarium. This particular sump is approximately 68 UK gallons and holds enough media for well over 1000 gallons, probably close on 3000 gallons to be quite honest. It has two Eheim 1262 pumps installed which each circulate 3400 L of water per hour, although I use one at a time.

The majority of the biological media I use are called bac balls. These are small plastic balls with lots of prongs sticking out. The surface area of these balls are very efficient for bacteria growth. You also have the added advantage that these do not get dirty like some other media.

This photograph shows the four chambers in my sump. No:1 chamber contains bac-balls topped of with mechanical filtration in this case filter matting which is very coarse and stops the debris but doesn't get completely clogged up too quickly. The water enters the first chamber and flows down through the media and then underneath the divider into the next chamber. It is vitally important that you leave a void at the bottom of your sump directly under your media. If your sump is designed so the water flows down and then underneath into the second chamber then you need to make sure that this space is not obstructed in any way. If this void does get obstructed then this can seriously inhibit the performance of your filter as the flow of the water will be restricted. There are various ways of making sure you have a void underneath your media. Probably the easiest way is to use a filter grid. These can be cut to size so they fit snugly in the bottom of your sump. Your biological media then sits on top and you have a nice space underneath for your water to flow easily and without restriction.

No:2 chamber contains more bac-balls biological. The water flows up through this media and then over the divider into No:3 chamber which contains Alphagrog. Finally the water flows through this biological media under the third divided and into the largest No:4 chamber which contains both Eheim pumps. The water is then returned back to the tank. One of the pumps itself circulates 3400 L of water an hour

To enable free water flow and to avoid obstructions a void should be created underneath the media

Now as I have mentioned previously not every sump is installed and set up in the same way so I can only really give you an example of how my particular sump is installed and how it works. I have got two reservoirs built into each corner as indicated by the No:1 on the left-hand picture. Running up inside this reservoir is a pipe as indicated by a No:2, also on the left-hand picture. This is the return pipe that brings the water back from the sump into the tank. Located at the bottom of the reservoir is a hole indicated by No:3. Inside the cabinet connected to the underside of this hole is a pipe that leads to the sump. Water flows over the top of the reservoir and enters the sump through this hole.

Now if we take a look at the right-hand picture the inlet nozzle slightly submerged under water as indicated by No:2. The reason this is submerged, rather than above the water is because the strength of the water entering the tank creates a lot of noise so to quieten things down I have submerged the nozzle. are still quite a lot of surface agitation and plenty of oxygen is being created in the sump and also the reservoirs. You can just see the reservoir indicated by No:1. When the water in the main tank reaches the lip of this reservoir, it will start draining into the reservoir. It is important to switch the pumps off when doing a water change. If you don't, you will actually remove water from the sump before any water starts being removed from the main tank.

It is very important that you choose a suitable pump for the size of your aquarium. Don't worry too much about getting a pump that may have an output that far exceeds the size of your aquarium. You must make sure that the pump that you use is powerful enough to circulate the water at least twice an hour if you are keeping large messy fish like Oscars. It wouldn't even hurt if the water circulated more than twice an hour. Also look at the head delivery of the pump that you choose. Whereas some pumps may have an impressive output of 3000 gallons an hour, they may only cover delivery head of 1 m. So what exactly does this mean? Basically it is how high your pump can push the water. So if you're using a large aquarium and the top of your inlet pipe is 5 feet above your sump then you obviously need to make sure your pump is powerful enough to push the water of this high, a pump with a delivery head of 1 m may struggle. The pumps I use have a delivery head of over 3 m and an output of 3400 l/h

Most of the pipework will be hidden away in the cabinet so you shouldn't have pipework at the back of the tank to contend with. The picture above shows the pipework in the left hand side of my cabinet, I have exactly the same pipework on the other side of the tank because I have two inlets and outlets. No:1 is a shut-off valve which can be used to stop water entering the sump from the tank, this can come in handy if you are carrying out extensive maintenance on your pipework and sump. No:2 is the pipe that is attached to the outlets, water travels down this pipe into the sump from the tank. No:3 is the pipe that it is attached to the pump, water travels up through this and back into the tank from the sump. No:4 are heater modules that are placed in-line from the pumps. This can often be a very efficient way of heating your water. If you cannot obtain heater modules then it is perfectly okay to put your heaters either in the sump, or in the aquarium.

If you do decide to purchase an aquarium that has been adapted to house a sump filter, bear in mind that the tank itself may have been drilled, in other words it may have holes in it. Even if you don't want to use the sump on the aquarium, it's quite easy to buy components that will shut off and seal the holes. Just don't take out the pipework and fill the tank with water because you may find all the water pours of the holes if you have not sealed them properly.

One of the drawbacks when using a sump filter is it is not so efficient when it comes to mechanical filtration. Unlike other filtration systems such as canister filters which use a pump to both remove & return water back to the tank, sump filters do not work like this, they only utilise a pump to return the water from your sump, the water flows from the tank using the force of gravity. It may be a case that you need to install a large canister filter if you are finding that a lot of debris is being left in your tank.

Don't underestimate your sump filter and assume that just because it is very big it doesn't need cleaning. Whereas they can be left for much longer between cleaning, they will slowly collect debris and crap from your aquarium and if you don't clean them they will actually start working against you which could mean poor water conditions.

Remember that a properly designed sump filter has got absolutely bags of room inside so utilize all of that space for both mechanical and biological filtration. Consider putting mechanical filtration in the first chamber, or even better put different types of mechanical filtration in the first couple of chambers. You can use filter brushes in the first chamber and then filter matting with some filter wool just to catch the last little bits. A large sump filter will take an incredible amount of biological media. To put it into perspective a 70 gallon sump filter will take 2000 and 20 kg of Alphagrog with plenty of room to spare. Removing all of this media by hand take a long time. You may save your self a lot of hassle if you contain all of your media in media bags. Basically instead of the media being dropped straight into the chamber, it is contained in bags so you can lift it out quite easily if you need to clean. We have already talked about sump filters not being the best mechanical filters that you could insert a power head into your aquarium to help stop debris settling. However if your overflow boxes other type where the water flows over the top then you may find that not all of the debris is removed quite as well as a large canister filter would perform.

My sump is a very basic sump design and to be quite honest it could have been designed a lot better. However it does the job so that is what counts at the end of the day. When you design your sump, bear in mind that in many cases it is going to be located under your aquarium where there will often be limited space. Sump filters normally have to stay in situ so design your sump so you have easy access to it.