Easily the most versatile type of filter, the aquarium sump allows for nearly endless customization, easy maintenance, and increased stability. An aquarium sump enables the aquarist to modify their filtration to meet their aquarium needs. The open design also allows for easy access to equipment and cleaning. Additionally, the sump provides a volume of water unoccupied by living organisms, creating a buffer which leads to a more stable aquarium system.
In its simplest form, an aquarium sump is a smaller tank made from acrylic or glass that fits underneath or near the main display tank. Water flows into an overflow box located in the main display tank, then down a drain pipe and into the sump, where it then passes through various filtration stages before a pump returns it to the main display tank.
Aquarium Sump Design
The fundamental design of an aquarium sump’s flow starts with the overflow’s weirs, positioned at the top of the overflow box, near the top of the display tank. As the water is pumped back into the display tank, it simultaneously flows through the overflow weirs and into the overflow then is gravity-fed into the sump.
Plumbing Redundancies
A well-designed aquarium sump system incorporates redundancies to prevent flooding. There should be at least one standpipe in addition to the drain pipe in the overflow box. The drain pipe is the primary conduit for water flowing into the sump. If the drain pipe becomes clogged, the stand pipe will accept the overflow and safely divert water into the sump, preventing the main display from overflowing. The overflow box, standpipe, and proper positioning of the return outlets also prevent the main display tank from draining into and overflowing the sump incase of a power outage when the return pump fails to pump water out of the sump. The aquarium sump should normally run with enough empty volume to accommodate the amount of water that flows into it when the return pump is off, without overflowing.
Diversity in Design
The total number of aquarium sump designs and setups are virtually limitless. Their versatility and customization even amongst pre-fabricated designs are expansive. Additionally, sumps can be designed and built by just about anyone.
The one factor that is consistent amongst all aquarium sump designs is the use of baffles. Baffles are dividers placed throughout the sump at varying heights. Their purpose is to separate the sump into multiple sections for filter media, equipment, and the return pump. More advanced sump designs include attachments in some of the sections to accommodate thermometers, water testing probes, heaters, and dosing tubes.
Physical Filtration in Aquarium Sumps
As the water passes into the overflow box and down the drain and stand pipes, it empties into the first compartment of the sump, where physical filter media are housed. The most common type of media is a filter sock or fleece roller.
Aquarium Filter Socks
Aquarium filter socks are made of 50-200 micron felt or nylon in which water passes through, trapping solid particles. Filter socks will collect any solids smaller than their micron rating. These are particularly effective because water cannot bypass the socks unless they become clogged and the water flows over the top.
Filter socks can be loaded in succession of micron rating. This method filters out larger micron debris first, then smaller sized debris as the water cascades to the next sock in line. Not all sump setups have filter sock holders in succession though, some are grouped to intake water simultaneously rather than sequentially.
Filter socks are only effective if replaced every couple days. Otherwise, organic material trapped in the sock decays in the aquarium water and passes into the system anyway.
Aquarium Fleece Rollers
A more effective alternative to the filter sock is the fleece roller. This device has a motor and a roll of fleece attached to a roller arm. The motor unwraps the roll as aquarium water passes through it. As the roll becomes soiled, it is unwrapped further as the soiled portion is coiled in the opposite end. As a result, no organic material which the fleece removes, touches the aquarium water, effectively removing organics permanently with no need to change the media every couple days.
Aquarium Floss Pads
Another common form of physical media is a floss filter pad. These flat square pads lay underneath the intake and stand pipes as water flows through them. They are effective, but some water is allowed to pass over the pad. Additionally, the pads typically have a higher micron rating, allowing larger particles to pass through. Some pads are infused with carbon or other nutrient- adsorbing compounds.
Depending on the number of compartments, additional physical media can be placed throughout the sump. Some aquarists use foam blocks in-between the baffling right before the return pump chamber to prevent any sediment from the biological filter chamber or refugium from entering the return pump and damaging the impeller or flowing into the display tank. Foam blocks placed in this area also serve to remove microbubbles produced by the skimmer before they can enter the main display.
Chemical Filtration in Aquarium Sumps
Due to the versatility of an aquarium sump, chemical filtration can be expanded to include more than just resins in mesh filter bags. Within the center chambers, reactors can be installed to maximize reaction time with media.
A reactor is a device that houses nearly any type of chemical filtration media, such as granular ferric oxide, (GFO), carbon, zeolites, bio-pellets, and others. The reactor is fed water from the aquarium then churns or tumbles the media inside its chamber. This increases the amount of time the media is in contact with the aquarium water, allowing for significantly higher rates of adsorption before the water is returned to the sump.
Reactors can be fed water from a dedicated pump or a manifold plumbed into the aquarium’s main return pump. The latter frees up room in the sump, produces less heat, and is one less electrical component to plug in.
The center chamber(s) can accommodate a protein skimmer. Some aquarium sumps will allow for flow control of the protein skimmer chamber allowing adjustment of the water level, which is crucial to maximize the efficiency of protein skimmers with an AC pump. Alternatively, you can use a skimmer stand to adjust the height of the protein skimmer. If your protein skimmer has a DC pump, the water level should still remain stable, but the DC pump has control over the efficiency as well.
Biological
Smaller aquarium sumps may have a portion of the sump available to store some biological media. Larger sumps have an entire chamber designed for either biological media, or a refugium. In saltwater aquariums, live rock can be used as the biological media, due to its highly porous nature, in both the main display tank and the sump. Manufactured bio media can also be used in addition to live rock or as the primary bio media in freshwater or saltwater aquariums.
Refugia are excellent biofilters when outfitted with a refugium light and constructed in the correct way. Refugia grow macroalgae which is efficient at pulling nutrients from the water and house live rock. Refugia also create a safe haven to allow the reproduction of food microorganisms such as copepods and phytoplankton.
To accomplish all this, the refugium needs a layer of sand or mud, some live rock or other porous material, and a light. Adding a foam filter after the refugium chamber is recommended to prevent silt and debris from entering the main display.
Aquarium Sump Cleaning and Maintenance
Maintaining sumps is fairly straightforward. When performing regular water changes, rinse or replace any filter media as necessary. Be sure to unplug any heaters if they are exposed to air during maintenance.
Chemical filtration should be replaced as directed based on the bio-load of the aquarium. Empty and clean out the protein skimmer collection cup. Biological filtration should be left alone. Macroalgae in the refugium can be trimmed when it becomes overgrown and begins to shade itself.
To clean the sump itself, scrape any precipitate or growth off the sides of the sump walls. Then use a short hose to siphon debris from the bottom of the sump. This is most effective when the return pump is off and the sump’s water volume is higher than normal as the gravity fed siphon will be much easier to start, have a higher flow, and allow more time for the removal of more debris.
Is an Aquarium Sump Right for Your System?
Sumps are a great option for aquarium systems that require more than the bare minimum for physical, chemical, and biological filtration.
Sumps are extremely versatile, easy to maintain, allow for nearly limitless customization, and create more stable aquarium systems. If you're a hobbyist who likes to tailor your system to your exact needs, a sump is a great choice.
Not all sumps need to be a separate tank plumbed from the main display. All-In-One aquariums include a smaller sump-like chamber in the back of the main display that functionally serves the same purpose as a sump, but with limited space.
Sumps may not be the best fit when you are limited on space, don’t have a pre-drilled tank with an overflow, or are using CO2 gas injection in a high-tech planted tank. In an open sump, CO2 will gas off quickly and it is difficult to achieve the necessary concentration required for high-demand plants. In this case, a canister filter with an inline diffuser is a better fit.
Feel free to contact us as Boodleshire Aquatics if you have any questions about designing your perfect aquarium sump.
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