A Buyer's Guide to Sump Filtration

Purchasing a sump doesn't have to be confusing or difficult, so long as it fits, it's probably going to work. That said, there are some considerations that will ultimately dictate your long-term satisfaction with the use of a sump on your reef aquarium. We broke things down into a set of 5 unique aspects that will ultimately help you make the best possible choice. 

1. Sump Size

There are two major factors that will dictate the size of your sump - sufficient capacity and available space.  A sump should be no smaller than 25% of your display aquarium's total water volume.  For a 100-gallon tank, you need a sump that can hold at least 25 gallons of water. With that in mind, the bigger the better is the motto when it comes to sumps. You really should choose the largest sump within your budget that fits into the space you have.

Ultimately, you want a sump that will hold all backflow of water that comes from your display tank when the return pump is not running.  Most sumps will operate around 50-60% total capacity when the return pump is ON so when it cuts OFF, there is plenty of room for backflow water to drain into the sump without overflowing. 

A sump, obviously, must fit underneath your tank or wherever you plan to install it. If you are retrofitting a sump inside of a tank stand, you also need to be able to fit the sump through the stand doors or access window. If your tank is already stocked and filled with water, this is particularly important because you probably cannot move the tank or slide the stand around making more room to slide the sump into place. 

All sumps have advertised external dimensions and give yourself at least 1" clearance on all sides to be absolutely certain the sump fits where it needs to be. If you have to measure your tank stand, break out the measuring tape and measure the available footprint (length x width) inside your tank stand.  The height is usually not an issue but still should be measured, especially if you have hard PVC plumbing or additional equipment inside the tank stand. 



2. How Many Chambers?

Sumps utilize special partitions called baffles to create the chambers and direct the flow of water through the sump. These baffles are what differentiate a sump from a basic container that holds water and a pump. They ensure water follows a particular path and comes in contact with your filtration equipment and media in a particular order. 

For the most part, you will be choosing from either a 3 or 4 chamber sump which covers 90% of the manufactured sumps on the market like most of the options from Trigger Systems. There are also more complex sump systems like those from the Hmhali brand that include additional chambers and configurations for media, heaters, and probes but these are really the exception.  

3 Chamber Sump

  1. Drain chamber
  2. Skimmer chamber
  3. Return pump chamber

4 Chamber Sump

  1. Drain chamber
  2. Skimmer chamber
  3. Refugium/Auxillary chamber
  4. Return pump chamber

5+ Chamber Sumps

  1. Drain chamber
  2. Skimmer chamber
  3. Refugium/Auxillary chamber
  4. Media chamber
  5. Return pump chamber

The exact flow of water and baffling will vary from brand to brand and the most important decision is to simply ensure your sump has the necessary chambers your going to need. Furthermore, the size of each chamber will be a limiting factor for the equipment you choose.  In other words, your return pump has to fit inside the return pump chamber, the heater has to fit somewhere, the skimmer has to fit into the skimmer chamber, etc.  If you already have some equipment in mind, be sure the particular chambers are going to accommodate said equipment. 

Sump System at BRS

3. What Features Do You Want?

Very much related to the chambers, there are a plethora of additional features to consider.  These would be things like filter socks or an automatic fleece roller, probe holders, ATO sensor mounts, heater mounts, cord clips, etc. Of course, expect to pay more for the more feature-rich sumps and the key is finding that balance of cost and the features that matter most to you.

Here are just a few questions that will help you narrow down the choices based on available features. Consider everything you know you want and then decide if anything extra is worth it. 

  • Do you want filter socks?
  • Do you want a built-in filter roller or do you plan to install one yourself?
  • Do you plan on using a dosing pump or monitoring probes?
  • Do you want a refugium?
  • Do you plan to use a media reactor or filter media bag?
  • Do you want some kind of mount for your heater?

Keep in mind, that you can still use a media reactor even if your sump doesn't include one or have a dedicated chamber for it. You will simply install the media reactor of your choice right alongside your protein skimmer. You can install probe holders in your return pump chamber or attach dosing tube holders pretty much anywhere. The point is that sumps are very customizable and if you are budget minded, a basic 3-chamber sump will still get the job done and can easily be customized as you progress through the hobby. 



4. Plumbing & Connections

The final consideration is your plumbing, most importantly how it connects to the tank. The location of the drain connections is probably the most important factor here because you don't want a sump that has the drain connections on the left side for a tank that has the overflow box on the right side. You really want the shortest distance possible between the tank drains and sump connections.

  • If your tank has two drain pipes but the sump only has one connection, how are you going to make it work?
  • Does the drain connection match the diameter of your tank's drains?
  • Do you have enough clearance, above the sump, to install your desired plumbing? 

With the use of adapters and flexible tubing, you can probably make it work in 99% of situations, but why not choose a sump that comes ready for easy connection to your tank without the hassle of complicated plumbing?