If you’re planning on setting up a reef aquarium or making an upgrade, you’ve heard of filter sumps and refugiums. But do you know what these terms mean?
A filter sump can be a refugium but a refugium isn’t really a filter sump.
Well, there are a lot of ways to do each but let’s start off with a brief history of filter sumps and refugiums. The original filter sumps were designed to be primarily for biological filtration.
They were referred to as wet-dry and trickle filters. Here’s why.
Wet-dry and Trickle Filters
Made of clear acrylic, the sump was positioned underneath the aquarium. It was shaped like a rectangular box capable of holding 10 or more gallons of water.
On top of the sump was mounted a one-cubic foot acrylic box that contained plastic biological filtration media. The media sat above the water.
A water pump in the sump brought water up into the aquarium.
When the water level in the aquarium reached the proper height, it poured into an internal water overflow system, sometimes called a “skimmer box”, and piped down to the filter sump.
The incoming water sprayed onto the bio media and trickled into the sump.
The concept was based on industrial wastewater plants where very high concentrations of pollutants were biologically treated.
The wet-dry or trickle component was designed to expose the bacteria living on the bio-media to plenty of oxygen, maximizing removal of ammonia and nitrite.
It sounded like a good idea and looked really cool under a reef aquarium.
Aquarium experts and retailers told everyone a wet-dry filter was absolutely necessary to handle the ammonia and nitrite produced in a reef tank.
Reef enthusiasts spent more time watching the trickling water than their corals!
But a funny thing happened. Aquarists who had to bypass the wet-dry filter, due to a break-down, lack of parts or healthy curiosity, discovered the wet-dry filter wasn’t necessary at all. The high surface area on live rock provided plenty of space for beneficial bacteria to grow.
There was no need for a “super-charged” wet dry filter on reef aquariums. Reef aquarists started removing the biofilter section of the sump and found their corals thrived.
There was never an ammonia problem and in some cases nitrate levels dropped, thanks to the more effective in-tank biological filtration.
The wet-dry filter just about disappeared from the hobby.
But filter sumps never went away. They’re more popular than ever. Here’s what happened next.
The Berlin Method
Reef aquarists were happy to get rid of the noisy splashing, high evaporation rate and messy salt creep associated with wet-dry filters. But they really liked the idea of a filter sump.
The modified wet-dry biological filters eventually became known as filter sumps. Aquarists liked the idea of having the extra room, outside of the aquarium, for topping off and keeping the heater out of sight.
Many sumps had internal baffles, making it easy to insert a filter sponge to capture particulates, bags of activated carbon and other specialty media.
German aquarists took it one step further and added external protein skimming as a major filtration component. This became known as The Berlin Method.
Eventually the filter sump became the central location to connect external devices like large protein skimmers and media reactors. The open sump provided an easy way to plumb all the new, high-tech hardware into the aquarium, without having to run multiple hoses up and down the back of the aquarium. But there’s more to the sump story.
Today’s automated aquarium devices with remote monitoring and control through smart devices are commonplace. But long before Wi-Fi existed, DIY electrical engineers were experimenting with electronic sensing of water levels.
With a sump, the water level in the aquarium stays the same. But the water level in the sump drops due to evaporation. If the water gets too low, the return pump will start sucking air and possibly burn out.
Many aquarists had allowed the water to evaporate and experienced damaged impellers and over-heated pump motors. By mounting a water level sensor inside the sump, it was possible to automatically add top-off water using a small dosing pump.
The early models were bulky and finicky because they were pieced together with industrial components. But today we’ve got highly refined, purpose-built water sensors and automatic top-offs (ATOs) designed specifically for filter sumps. But the sump revolution didn’t stop there.
Protein Skimmers and Filter Sumps
A protein skimmer is considered a necessity for maintaining water quality in a reef aquarium.
Removal of dissolved organics before they break down into nitrate and phosphate goes a long way to improve water quality and overall health of SPS and LPS corals.
If you wanted a protein skimmer in the past, it had to be positioned next to the aquarium. It was a complicated install because the skimmers were tall, needed a separate water pump and a lot of adjustment to keep them running properly.
But with the popularity of filter sumps, protein skimmer manufacturers began designing shorter skimmers for placement inside the sump.
Today’s skimmers have built-in DC-powered water pumps that are small and efficient. Better yet, the motors are perfectly matched to the skimmer. Just drop the skimmer into the sump.
With a filter sump and in-sump protein skimmer, hours of tweaking and adjusting to dial in the skimmer are over. But there’s one more advancement that needs to be mentioned.
DC Return Pumps
In the early days of reef-keeping, we had to use water pumps that weren’t intended for aquarium use. Most pumps were scaled-down industrial units.
They used a lot of electricity and generated quite a bit of heat, sometimes affecting the tank’s water temperature.
External water pumps were often noisy because their motors were meant for manufacturing and construction applications.
Today we have purpose-built “return pumps” designed for aquarium use. They’re smaller, quieter and use less energy.
The DC current motors can be controlled with a wired controller or through a wireless smart device. The advantage is you can reduce the flow by slowing the motor.
Traditional water pumps simply get “choked down” with a valve, causing the motor to try to push water through the obstruction.
With DC water pumps, you can even program the water flow to stop while your feed the fish and corals.
What is a Refugium?
An interesting thing happened while filter sumps were being perfected by reef aquarists.
The concept of the refugium was also becoming popular.
Think of it as a tiny aquarium and light, connected to the larger, main aquarium.
A reef refugium provides an isolated environment, separate from the reef tank, for growing macroalgae and culturing live rock for biological denitrification.
Here’s how it works. Water from the main reef tank is pumped through the refugium at a slow flow rate. As macroalgae grows, it removes phosphate and nitrate, lowering nutrient levels in the water.
Pieces of rock rubble provide a place for macroalgae to attach to. The live rock also provides a porous surface for colonization by microbes. Bacteria in the rock pores remove nitrate through natural denitrification.
Some aquarists add a thin layer of sand, so worms and burrowing organisms have a place to live.
Because the refugium is isolated from the fish and corals, it acts as a live food “factory” by providing a safe space for amphipods, copepods and other microorganisms to grow.
The circulating water periodically sends the live foods out of the refugium and into the aquarium for consumption by fish, corals and other invertebrates.
Filter Sump meets Refugium
Before long aquarists noticed that they could create a refugium section inside their filter sump. The baffles within the sump could be loaded with rock rubble for natural nitrate removal. Copepods and other live foods thrived within the rock pieces.
Some aquarists added a light on top of the sump just for growing macroalgae.
Periodic harvesting of the algae removed the nutrients from the tank and stimulated the macroalgae to regrow and adsorb more nutrients from the water.
This realization opened up a new world of possibilities of combining the filtration and hardware connectivity benefits of the filter sump with the biological benefits a refugium.
Fast forward to today and you’ll find an array of plug and play filter sumps with refugium capabilities.
Best Reef Sump & Refugium Reviews
You no longer have to piece together a home-made sump rig and hope it works. Manufacturers have taken all the best features and combined them into perfectly designed units.
But which model is right for you? We’ll take a look at a range of filter sumps with refugium capabilities to help you choose the best for your tank’s needs.
If you’re looking for a basic acrylic filter sump, Eshopps RS-series has you covered.
All RS sumps have 300-micron filter bags and a foam pad to trap protein skimmer microbubbles. All RS sumps use a three-chamber design.
The first chamber contains the filter bag(s). The center chamber is for a protein skimmer. The last chamber is for the return pump. There are four RS filter sumps: RS-57, 100, 200 and 300.
If you’d like to have a filter sump and refugium, Eshopps makes those too. The R-series refugiums combine the filter bag feature with a larger second chamber designed especially for refugium use. The water flow pattern is altered so it washes gently across the rock and algae.
- RS-75: Rated for 10-75 gallons - Dimensions: 18"x10"x16"
- RS-100: Rated for 75-125 gallons - Dimensions: 24"x12"x16"
- RS-200: Rated for 125-225 gallons - Dimensions: 30"x12"x16"
- RS-300: Rated for 225-300 gallons - Dimensions: 36"x14"x16"
- Well-built acrylic construction.
- Quiet operation.
- Wide range of sizes.
- Refugium option.
- Return side of the RS-75 is a little tight for many water pumps.
Trigger Systems is a US-based manufacturer of filter sumps, dosing systems and automatic top-offs (ATOs).
The acrylic sumps are hand assembled using top-grade acrylic and precision welding methods.
Trigger Systems sumps have rounded corners reported to increase seam strength. The beautiful color options (Ruby, Sapphire, Crystal, Emerald and Amethyst) look great underneath the reef aquarium.
The sump has adjustable baffles, making it easy for the sump to double as a refugium. The water height in the skimmer section can be adjusted. You can use filter socks or filter foam blocks for particulate removal.
Trigger Systems sumps come pre-drilled for adding an automatic top-off system.
These sumps are available in a wide range of sizes, ranging from the small 18” cube to the monster Triton 44” sump.
- Outstanding craftsmanship.
- Plenty of size and color options.
- Modular design makes customization easy.
- Quiet operation.
If you’re looking for a simple HOB refugium or can’t fit one under your tank, the AquaFuge 2 deserves a close look.
The AquaFuge 2 provides a secluded safe zone for live foods like copepods and amphipods, to feed SPS and LPS corals along with fish in the reef tank.
The optional LED light will allow you to grow macroalgae inside the hang-on fuge. The internal baffle system prevents sand and live foods from being washed out of the chamber.
The refugium comes with a Rio submersible pump, making it a plug and play set-up. The AquaFuge 2 is available in three sizes.
- Simple HOB design.
- Includes water pump.
- Multiple units can be used on large aquariums.
- LED light not included.
Located in Florida, Pro Clear Aquatic Systems is a large custom aquarium, filter and aquatic display company.
All Freedom series sumps have electric equipment wire holders and a probe holder.
The Freedom 4-in-1 offers has four filtration possibilities for reef aquariums; mechanical filtration with a 200-micron bag, protein skimmer chamber, chemical filtration when using the optional Chemical Media Cartridge, and biological filtration in refugium compartment. This sump is designed for quiet operation and uses a patented silencer design.
Four sizes are available.
- Freedom 100: Rated for up to 100 gallons - Dimensions: 16"x 16"x16"
- Freedom 200: Rated for up to 225 gallons - Dimensions: 32"x 12"x16"
- Freedom 300: Rated for 300 gallons - Dimensions: 37"x 14.5"x16"
- Freedom 400: Rated for 400 gallons - Dimensions: 45"x 14.5"x16"
- Well-built with quality fit and finish.
- Unique electric wire guide.
- Includes a probe holder.
- Quiet operation.
The Aqueon ProFlex series of three-chambered sumps are modular, meaning you can customize the set-up in several different ways.
The basic sump design uses two 200-micron filter socks in the first chamber of the sump.
Incoming water passes through the socks, for particulate removal. The modular design allows you to install an optional wet-dry biological rack that holds plastic biomedia. You’ll have to purchase the rack as an extra component and supply your own biomedia. Reef aquarists normally don’t use a wet-dry, but if you want one, it’s available.
For a Berlin-style filter, drop an internal protein skimmer into the second sump chamber and return pump in the third. It’s easy to add a refugium to the third chamber. Just add rock rubble and macroalgae along with a small LED light fixture. The ProFlex sump comes in four sizes.
- ProFlex 1: rated for 44-55 gallons - Size: 21” x 18” x 11”
- ProFlex 2: Rated for 55-75 gallons - Size: 30.9" X 11" X 19"
- ProFlex 3: Rated for 65-110 gallons - Size: 26.3” x 17.4” x 14.8"
- ProFlex 4: Rated for 120-210 gallons - Size: 36.9” x 19” x 14.8"
- Quiet operation when used as a berlin or refugium.
- Filter socks provide good particulate filtration.
- Works well as a refugium when a light is added.
- Limited lifetime warranty.
- Poor packaging has resulted in damaged panels and higher return rates.
Windrider Creations is a custom aquarium and stand company. They also design and manufacture acrylic filter sumps and refugiums. The hand-crafted sumps are made from ¼” thick acrylic.
The sumps are available as a complete, ready to run unit or in DIY kit form. The 50-gallon sump (45”x15”x15”) comes fully assembled and includes two filter socks. Two bulkhead fittings are included for connection to your overflow.
The large 20-inch water input chamber is designed to hold the socks and a large protein skimmer. The second chamber has plenty of room for a refugium filled with rock and algae. The return chamber has room for most return water pumps.
This filter sump-refugium is rated for aquariums under 200 gallons. If you want to build it yourself, The Filter Kit comes with pre-cut panels. Glue the pieces together to form a 30”x12”x15” sump and refugium. The DIY kit doesn’t include filter socks or inlet hardware. But if you’re confident about assembling your own filter sump, you’ll be able to add your own custom water inlets and filter socks.
The DIY kit includes detailed instructions, product support and even a how-to video on YouTube.
- Hand-cut and fitted.
- Reliable build-quality.
- Custom sizes available.
- DIY option.
- Limited in-stock sizes.
Most aquarists want to purchase a proven sump design that works without making any modifications. Fortunately, all these sump-refugium products meet these criteria.
The Eshopps filter sumps are basic designs with no fancy extras.
Trigger Systems offer luxury sump-refugium units that are beautiful and functional. They’re popular with reef aquarists who build their aquariums to include automatic top offs and other automation sensors.
If you just need a refugium, the CPR AquaFuge 2 is a proven performer. Simple and effective are the trademarks of this HOB refugium.
The best advice for selecting a sump or refugium is study the specifications to make sure it will fit into the aquarium stand. Then check the chamber dimensions to see if your return pump and protein skimmer will sit comfortably inside.
Some manufacturers off a wide variety of add-on designed to drop into their sumps. Then compare what features are available for the sump models that fit. Some designs are bare bones while other have many optional add-ons that make reef-keeping easier.
If you have any questions or comments on sumps and refugiums, please post them below!