Aquarium Sump & Refugiums: Five Higly Recommended Low-Noise Brands

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.

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.

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.

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.

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.

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.