A sump is nothing more than an extra water containment area usually set up underneath an aquarium where you can place equipment, provide the aquarium with various types of water filtration, add top-off water to the tank and perform other maintenance tasks. For a more in depth explanation on what the design and function of a sump box is, Robert Metelsky explains this very well in his Simplified Reefkeeping Sump Box FAQ, where he outlines a two chambered sump.

From the simple single chamber design to the more complex multi-chambered set ups, sumps are quite versatile. Just take a look at some of these DIY examples.

• Dog's sump set up has a prefilter pad with bio ball chamber and complete live sand refugium incorporated into it.
• Peter Z.'s sump design is three chambered, with the middle chamber containing bio-media for biological filtration.

As you can see from these few examples, there are just as many sump set ups as there are aquarists who design them, and you don't have to buy one either. Glass or acrylic aquariums and plastic containers can be converted into sumps very easily, or you can always build your own from scratch. However, for those of you that may not be do-it-yourselfer types, pre-manufactured sumps are available on the market.
What are the benefits of having a sump?

• It makes an ideal place to put a protein skimmer ( read reviews & compare prices), heater(s), and other equipment such as a calcium or nitrate reactor, because you don't to figure out inventive ways to hide all this stuff when hung on the outside or placed inside an aquarium, and it saves on space.

• It is an ideal place to put bio-media for biological filtration, as well as perform additional mechanical and chemical filtration.
• It is the perfect place for dosing supplements. Topping off tank water and adding limewater (a.k.a. kalkwasser/calcium) or other additives to a reef tank goes hand in hand with a sump, because one of the dosing methods most often used by aquarists for introducing limewater into the tank is done by way of the water in the sump. This is usually accomplished by using a slow drip water top-off set up, or an auto-doser or metering pump.
• It adds additional beneficial tank water volume to your system.
• It can provide additional aeration to your system.
• It can contribute to improved quality of the aquarium water.
• When set up properly, it can act as a back up water overflow system if the power fails.
• Add the DIY Auto Top Off to your sump to eliminate the hassle of repetitive top offs.

When running a reef system, some people find that bio-media in a wet/dry trickle filter becomes unnecessary when adequate live rock is provided for biological filtration. For this reason some aquarists choose to remove the bio media and convert the trickle filter into a plain sump for holding carbon, or use it as a water reservoir/top-off area.
Do you need a sump?
In our opinion it is a personal choice of whether to have a sump or not, but with the many benefits one can provide your system, along with how easy it really is to put together, why not?

Here are some more DIY Sump Projects & Plans you can use to build your own. You can also see what is available on the market in the Top Wet/Dry Filters. To learn more about how to set up a sump, refer to our Sump & Overflow Set Up Resources and take time to cruise through our Reef Tank Photo Galleries to visit personal saltwater Websites to see how other aquarists have set up sumps for their systems.