Sumps are used in most off the shelf marine aquariums nowadays but why? What purpose do they serve and how easy are they to maintain?
Basically, a sump is another tank that is housed either in the cabinet below the display tank or remotely (for example, in another room) and are used for enlarging the system volume and keeping filtration equipment out of the display tank.
They work by having a series of glass or plastic/acrylic baffles which divide the sump into chambers for different methods of filtration. Water from the display falls down a weir or overflow via pipes towards the sump. We can explore what happens next…
Typically, the water from the tank would pass through a prefilter first. This should be something easy to remove and clean so that detritus doesn’t break down in the sump causing water quality issues. The most popular method is filter bags or socks. These products are made from material or nylon and vary in size and porosity. These are very good at catching anything passing through them, but the downside is they do need regular cleaning as they block up quickly depending on free floating detritus. Other aquarists use a series of sponges that the water must pass through. These are also great at catching particles but will still need some maintenance although less that the filter bags. I currently use a plastic rectangular planter that hangs inside the sump on the back pane. Holes have been drilled in the bottom to allow the water to pass through and a couple of holes near the top in case the sponges inside the planter block up and the water overflows. I have packed it with sponge only, but you can go as fine as filter wool if you don’t mind removing and throwing it away on a weekly basis. This method is working very well for me and in fact is very easy to look after.
In this first chamber I would also look to place the protein skimmer. My reasons for this are as follows:
• The skimmer can catch anything that passes through the filter bag.
• Bubbles from the skimmer normally dissipate by the time the reach the later chambers of the sump meaning they don’t end up in the display.
• Storing the skimmer here leaves room in other chambers for other filtration.
In the second chamber you can utilise several different methods depending on what you are trying to achieve in the display tank. Some people prefer a refugium here - a place where marine algae or seaweed is grown - in order to lower nitrates and phosphates. This can be done using a mud substrate. I have used this method in the past and found it to work well. However, a layer of silt or detritus can and often does, collect on top of the mud and it is very difficult to siphon this out without removing portions of the mud. With this method you tend to get brown, red and green algae on the surface of the chamber as the water flow is slow where the floating algae bathes under the refugium lights. You may also get algae die off below the surface, so regular movement is important if choosing this system.
A pet hate of mine is to cram chamber 2 with live rock, alfa grog, bio balls and other biological media. If you are using enough quality rock and sand in the display you are simply creating another area for detritus to build up. You will only house enough filtering bacteria in the system relative to the waste being created regardless of how much media you are using. I have witnessed many a tank with a few fish but tens of kilograms of rock in the sump and display to filter the water. It is simply not needed.
I would much rather place reactors in this section. Yes, they have an additional cost and need pumps to run them, but you can be clever with your pumps which I’ll explain further later.
If you prefer to run the system as naturally as possible then I would consider a REEF Bio-Gro reactor, which has a light in the middle. You place some algae in the reactor and attach a slow pump that feeds water to be filtered through the algae. The intense light grows the plant material, but you don’t end up with any of the disadvantages referred to in the earlier refugium section.
You could run Tropic Marin Bacto Pellets which I have found to work wonders with heavy stocking and feeding aquariums. These pellets are essentially a food source for bacteria to grow on which in turn consume nitrate and phosphate. The only real maintenance is a yearly top up of pellets when they have depleted.
Yet another reactor can be used for phosphate removal media and/or carbon. This removes not only phosphate but can remove silicates and water colour and impurities.
If, like me, you use a man-made rock and still think you need more in the way of biological filtration, a cleaner way of achieving this is to use a sand filter, such as the REEF-Filter Bio. The sand that is agitated inside the reactor tube has a massive surface area but, because it is always on the move, it stays very efficient and clean with zero maintenance!
Chamber 3 is simple, as this should only have a return pump and your auto top up float switch. The water level in this section can move up and down depending on evaporation so best to house the float switch for the auto top up in here.
As far as return pumps go I would 100% consider a REEF-Pump from TMC. These pumps have proved to be super quiet, super-efficient and super reliable. I would encourage anyone thinking of buying one to always spec for the model above the one you need as running the pump on one of the lower settings results in less energy consumption than running a smaller pump on full. This is less taxing on the pump also and helps them run cooler. A smart way to power not only your water return to the main tank but also all the other reactors or a UV steriliser would be to go for a much bigger pump than needed for the return alone and build a simple hard pipe manifold that attaches to the bigger pump - imagine fittings coming off the top of the pump with a few adjustable taps (like hosetails) from which each reactor etc feeds. You can then adjust the flow into each reactor/UV separately and accurately, as well as the return to the display tank all with one pump. This certainly cuts down on having lots of pumps and plugs and is good for sumps where space is limited.
The last thing to consider is UV, ozone and dosing units. Ozone would always be fed into the skimmer in chamber 1, minimising any ozone reaching the display. A dosing unit would be better dosing as far away from the skimmer as possible so chamber 3 would be the best option. Finally running a UV for parasite prevention and suppression should be the last stage of filtration to minimise exposing the quartz sleeve to dirt etc which would hinder its performance.
I hope this has helped to explain how a sump can be used ... I think a sump is a great addition to any aquarium but does need regular upkeeping to make sure it works to its full potential.