To sump or not to sump?

Taking the mayhem out of marine fish keeping


to sump or not to sump?


The majority of marine fish keepers will tell you that a sump is an essential piece of kit and that you can't keep a marine tank without one. It's like many things, once you have one you can't imagine life without it but there are plenty of people keeping amazing marine aquariums without the benefits of a sump


A sump is an additional tank often kept under the main display tank and linked to it via a series of pipes. It works on gravity so no matter where it is located it needs to be lower than the water level in the main display tank.


There are many benefits to a sump, it increases the volme of water in your system (remember the larger the volume of water the more stable and forgiving your marine tank will be)


They also offer great flexibility as to where you can hide all sorts of wierd and wonderful kit from reactors and algae to heaters and protien skimmers. They provide a handy place to add any water for top ups, water changes and any additives you may use and can help to increase airation (therefore oxygen) in your tank water.

There are many different types of sumps, some more complicated than others but they all share the same basic features. A sump is a tank that is split into often different sized chambers by a series of partitions called baffles. It receives water from your display tank which reaches it by travelling down an overflow fitted onto the main tank.


If you are going down route of a sumped tank you may be better off going for a pre-drilled tank that is already prepared to take all the associated pipework and plumbing that will be necessary. You can get 'Hang on Back' (HOB) overflows that will work but these often rely on a syphon to work, if the syphon is broken you will end up with a very wet floor....


Water travels down the overflow, into the sump and passes over, around or under any of the baffles present. Whilst doing so it will go through any equipment or media you happen to have in there, such as live rock, algae beds, deep sand beds, protein skimmers and reactors. After the water has been through the rollercoaster of the sump it is pushed back into the display tank by a return pump to be recirculated and end up trickling back down the overflow ready for the whole process to start again.


Sumps certainly have many benefits (although they can be a bit noisy) but if you are considering marine fish keeping on a budget you need to consider the cost implications when getting into the realms of drilled tanks, plumbing and extra electrical equipment.


You can certainly run a beautiful marine tank without a sump (you might just have to consider the positioning of the equipment within your tank a little more carefully). On a side note if you are going for a simple and/or cheaper marine tank then you will likely get away without running half of the kit that sumps are designed to take.

Helpful tips




If you are still considering where to put your tank remember to allow for the extra weight of the sump!


If you run a sump always check the overflow regularly because at some stage or other some of your marine tank inhabitants will make it their personal mission to get stuck down it.

Sumps - in a nutshell

They work by drawing water in from your display tank, pulling it through allt eh various bits of kit in the sump then pushing it back into the display tank again

They are great for hiding lots of unsightly kit

They add to the overall volume of water in your marine tank therefore making it more stable and more forgiving of any mistakes you may make in the early days

Remember sumps mean additional pieces of eqipment so if you are on a very tight budget you may want to think twice.

You may want to consider a pre drilled tank rather than HOB overflows or DIY