So what exactly is an aquarium sump filter? Sump filters are large filters that are normally located under the aquarium. Sump filters can hold large amounts of biological media, thus making them capable of processing large amounts of water very quickly.  If your tank is less than 100 gallons, a sump filter isn't really practical, they come into their own when used on multiple tank setups, shop displays, or very large home aquariums. The majority of them are constructed out of a normal fish tank. Dividers are attached inside the tank so that you have various chambers. Each chamber can contain various types of media plus heaters and pumps.  The majority of Sump filters can have anything from two, to five chambers depending on the size of the aquarium and the type of media you are using.

So what are the advantages of a sump filter over other filters such as canister or hob filters? Canister or hob filters are only able to handle a set volume of water.  In other words, if you have a 100 gallon tank, you would need to find a canister filter that is rated for your tank. Sump filters on the other hand are only governed by the pipework and pumps you use . Sump filters are extremely flexible as you can put just about any type of media in them. They can also contain heaters and pumps saving you the hassle of installing them inside the aquarium. The one thing I really like about using Sump filters is the inlet creates a strong currents which oxygenates the tank more efficiently than any filter I have ever used. Using a sump filter means that you are adding that much water to your system.  It's much easier to maintain good water quality in a large tank, rather than a small one because fish waste is diluted much more in the large amounts of water. So having as much water to your system can only benefit you in the long run.

My sump has four chambers. The first two chambers contain approximately 1500 bio balls with mechanical sponge media on top in the first chamber. The second chamber also  contains two heaters. The third chamber is packed full with alfagrog, a very porous media that is extremely efficient at containing beneficial bacteria.  The final and largest chamber contains two Eheim pumps, although only one of them is in use, the other is a standby.

You may think to yourself, what happens if the power goes off and the pumps stop working?, will the water will keep draining into the sump and flood the room. Fortunately, if it has been set up properly, this can't happen. Before filling the main tank up, you first fill your sump making sure you leave enough space for any excess water to enter it. So if the pump goes off, the water will continue to flow into the chamber until the water level drops just below the edge and then it will stop. As long as you haven't put too much water in the sump beforehand, there shouldn't be any accidents. This is the way my sump is set up, others may differ slightly.

Installing a sump filter on existing aquarium is not the same as going out and buying a normal canister filter. Tanks need to be drilled before you can set up a sump filter. It would be virtually impossible to install a sump on a tank that is already running, you would have to completely empty it and start from scratch.  Also bear in mind that you need enough room underneath the aquarium. It's no good installing a sump if you can hardly get your hands above it once it's in situ underneath the aquarium.

Once you have been using a sump for a while, you will probably never go back to anything else. Sump filters are truly superb filtration systems that will keep your water in tip top condition and maintain your fishes health. 

Sump filters can be noisy

Now there is one important factor that must be taken into account if you are thinking about installing a Sump filter. These type of filtration systems can create a lot of noise, a lot noisier than your normal external canister filter. You've got to remember that you've got quite a lot of pipe work involved with a Sump filter. Most people who have sump filters use them on big tanks, therefore you have a lot of water running through the pipe work.  You may get quite a lot of gurgling as the water runs through the pipes.  Also, you normally use a fairly powerful pump in a Sump filter, this will increase the pressure of the water entering the tank which will obviously create noise as well.  However, this is one of the benefits of using these type of filters, you'll never have a problem with oxygen depletion.  I have also found that the fish enjoy the strong current that the powerful pumps create.  You can't replicate this with any other filter, unless you use some kind of power head.  I have read of some people who can suppress the noise with slight alterations but I haven't done it myself.

My big tank with a Sump filter is in my main room that I use on a daily basis, I have got used to it now, however you realize just how noisy theyare when you switch the pumps off when carrying out water changes. If you don't like a lot of background noise, do not install a Sump filter in the room that you use on a regular basis because it will drive you around the bend.  Just imagine having a very small waterfall in your room, that's probably a good way of explaining what a very large tank fitted with a Sump filter sounds like

Brief description of the sump filter