Understanding Sumps
If you're reading this article, chances are you've read about or heard of a mythical form of filtration common to the saltwater side of the hobby, the Sump (or you're a moderator
). I often see sumps recommended on this board and other similar ones around the 'net'. People suggest them often, but the foreign concept of a sump is confusing to many new aquarists and few good resources exist to help. As such I believe that many members write off sumps as too hard, or tell themselves they're too plumbing inept to create one. This article will attempt to explain sumps, their benefits and how they work. It will then help guide the new aquarist through the task of designing his/her own sump.Introduction - What is a Sump?
A sump is any tank which sits below the level of the main display tank. It holds more water for our tanks, and is a great place to house unsightly equipment. Things like heaters, protein skimmers, power filters, chemical reactors and more. When showing off our beautiful slices of ocean to others in person or over the 'net', nothing is more distracting than a background full of electrical wires and equipment.
The sump tank itself can really be just about anything that holds water. Converted glass aquariums, custom acrylic tanks, plastic bins, horse troughs or even garbage cans could be used as a sump tank. Most often the tank is placed underneath the stand of the aquarium for convenience and space-saving reasons, yet it's location is not set in stone. A sump tank can be placed next to the stand, it can be plumbed into a basement, or can even be plumbed through a wall into an adjacent room. Each type and location of tank has its advantages and disadvantages which I will touch on later when discussing individual setups.
Terminology
Terminology is always a tough one in the marine side of the hobby. So many new aquarists are often daunted by the different language we salties speak. Therefore a glossary of terms will be needed for the rest of this discussion:
- Drain Line - Plumbing that uses gravity to transfer water from the display to the sump
- Return Line - Plumbing that moves water from the sump back up to the display tank
- Return Pump - A submersible or external pump which pumps water through the return line and up to the display tank
- Refugium - A section of a sump used to grow macro algae to combat nutrients and provide a place to grow other beneficial life
- Bubble Trap - A series of walls and constructions within a sump designed to catch bubbles from the drain line and prevent them from entering the display
The Drain
Most new saltwater aquarists with questions on sumps focus too much on the sump tank itself. However the drain is the most important part of the system. A drain runs off of gravity to supply the sump. There are three basic types of drains:
Now the moment I bring up the word "drill", many of you readers cringe with foreboding. Fret not, drilling is much easier and safer than people think. Methods for drilling are the subject of another article.
Overflow Boxes
Overflow boxes are convenient overflows if drilling is not an option, or if the tank is already setup and running. As seen below, they consist of two boxes which hang over the edge of the tank, one inside, and one outside. A U-tube connects the two boxes and permits water to flow from the inside to the outside via a siphon. Then the exterior box has a drain which is plumbed down to the sump. As the water level in the display tank rises, water cascades into the internal box, bringing its level up. Then the siphon brings water over the glass wall into the external box. Water rises in the external box and cascades down the drain into the sump.
Overflow Box Diagram
The concept is simple but frought with two difficulties. Over time, the U-tube siphons can build up air bubbles inside them. When enough bubbles have collected, the siphon breaks and water will no longer flow to the external box. Ultimately the sump runs dry and the display tank overflows, both of which are bad things. The only way to prevent this is frequent checking of the U-tube to make sure dangerous air-lock conditions are not building up. The second drawback of a U-tube is noise. They often suck air and create many gurgling sounds. The aquarist can counter these problems by sticking a foam filter over the drain line which muffles the sound. However the foam filter MUST be cleaned regularly for if it clogs up, the same problem happens (empty sump, overflowing display).
All that being said, many people use overflow boxes with little trouble. One must however realize their limitations and care requirements before using one.
Durso Standpipes
If the aquarist resides in the UK, or is in the US with a bottom-drilled tank, a Durso Standpipe is the way to go. A quick note: >95% of tanks for sale in the US have tempered glass on their bottom. Tempered glass CANNOT be drilled, so all you US readers who don't already have a hole drilled in the bottom of your tank can skip to the next section on Calfo Overflows. UK tank owners, your tank bottoms are NOT tempered glass and bottom drilling is a good idea.
As mentioned above, the Durso Standpipe uses a hole drilled to the bottom of the tank which is fitted with a bulkhead fitting. A pipe is then affixed to the bulkhead pointing vertically to a level a few inches below the desired tank level. At the top of the standpipe a Tee fitting is secured with one end having an elbow pointing downward, and the other has a cap atop it. A small hole is drilled in the top of the cap (~1/8") to allow air to pass through it. The standpipe is covered with a 2-sided acrylic box which is siliconed to the tank walls and floor. This box acts as a barrier to keep out snails and other critters and to establish the display tank's water level. It is important that this box be sealed to the tank in the event of a power outage. This will prevent you from draining too much water into the sump. And the hole atop the standpipe keeps it quiet (removes gurgling sounds) and auto-starts the siphon when power comes back on.
For safety I will reccomend using two Durso standpipes (each capable of handling the entire flowrate) in any design. One slightly higher than the other. That way if a snail, or algae, or something gets into one stnandpipe and clogs it up, the second standpipe can take over and provide drainage until the blockage is removed.
Calfo Overflow
Last of the drain options is the Calfo Overflow (named after conservationist Anthony Calfo). Popular in the US, a Calfo Overflow is used when drilling the bottom of the tank is neither desired nor possible. Here, a side or back wall of the tank is drilled and fitted with a bulkhead a few inches below the water level. On the inside of the tank, a right angle fitting pointing downwards is affixed to the bulkhead. On the back side, a Tee fitting is used with one end connected down to the sump, and the other end capped off with a 1/8" hole drilled in it (similar to a Durso). Again, the internal workings of the overflow are surrounded by a silicone or glass enclosure to keep critters out and keep the tank looking neat. This internal box need not go to the floor of the tank, but may "float" with a sealed bottom. Again, as with a Durso, the box needs to be siliconed to the tank walls to seal it.
Here, as the water level rises in the display it gets above the internal overflow. It cascades into the box where the level fills up to that of the bulkhead. It then cascades downward into the sump. A very simple and elegant design. I employ a Calfo Overflow in my own system and it works wonders. Again, I would recommend that you have two drains in case something gets inside the box. I had a snail get inside my box and clog up the "main" overflow. I noticed this when the tank level was a little higher than normal. Had I not had the second overflow, that little rogue snail would have caused a lot of leaking and damage.
The Sump Tank
Now that we've discussed and chosen an overflow type, let's transition to discussing the sump tank itself. Sump tanks themselves can be as simple or as complex as the aquarist desires. The tank itself is commonly placed in the stand underneath the display, yet by no means is this a requirement. Sump tanks can be placed next to the aquarium perhaps in a cabinet, or under a table. They can be behind the tank in perhaps a fish/maintenance room on the other side of the wall. I have also seen plenty of tanks located in the basement (for those that have them) plumbed through walls/floors.
Whichever sump location is chosen, the space available will dictate the size of the sump tank. I generally recommend using the largest tank that can possibly fit inside the space available. When chosing a tank, consider its height as well since a sump that is excessively tall will be difficult for the aquarist to get his/her hands in to work on/clean the sump. And when it's difficult to do, we all know that we'll put the work off until it's more convenient. Speaking from personal experience, tall sump tanks may also be too tall and prevent the aquarist from fitting taller equipment (like skimmers, reactors, etc) inside it.
So what goes in the sump? Well, the choices are many and so I'll offer a list here that is by no means comprehensive:
By no means does one have to employ all these measures in their sump. In fact, employing every item in that list would be somewhat prohibitive/difficult in terms of both size and cost. As such, an aquarist needs to review their space limitations and make decisions on what equipment they need. I personally employ a protein skimmer, refugium, 2 heaters, a phosphate reactor, and a UV sterilizer all jam packed into a small 20 gallon long tank. Barely an inch of free space remains but it works well.
