Algae Scrubber

Used by more advanced aquarists, the algae scrubber provides an efficient and natural way to reduce nitrate and phosphates in the marine aquarium.

An algae scrubber, sometimes called a ‘turf scrubber’, is simply a plastic sheet or plastic mesh material, on which brown and green microalgae is encouraged to grow. Usually regarded as unsightly, nuisance algae, the microalgae here serves as a nitrate and phosphate absorbing sponge!

An algae scrubber is also a good complement to a refugium. When placed on a reverse lighting cycle, an algae scrubber, just like the macroalgae in a refugium, will help to stabilize pH at night.

Setting Up An Algae Scrubber

A small water pump directs water from one the compartments of the sump to the top of the plastic sheet to a spraybar, and is allowed to flow over the sheet and over the algae. A single light source, usually a simple 40w light bulb, is pointed at the algae to encourage it to grow.

Provided you have enough nitrates in your tank, a newly setup algae scrubber can take anywhere from 4 to 6 weeks for the algae to grow enough to actually start absorbing nitrate.

If the microalgae still has not taken hold after 6 weeks, you will need to increase the light intensity on the algae scrubber. Two 40w light bulbs (use their low energy consumption equivalents) almost guarantee a luxuriant growth of algae in a few days.

Nutrient Export

Export of nutrients is accomplished by literally scrubbing off some of the algae periodically. Removing some of the algae in this way also removes the absorbed nitrates and phosphates.

Only about half of the algae is removed at any one time so that new algae can quickly take hold and start growing again. Depending on the rate of the growth, the algae should be removed from the scrubber once every 2 weeks or once every month.

Algae Scrubbers And Phosphate Removers

Algae requires a sufficient amount of nitrates and phosphates for growth and very low quantities of each will result in the algae dying off.

Since the idea behind utilizing an algae scrubber is for very natural nitrate and phosphate reduction, using a phosphate remover is self-defeating as the algae is liable to die off.

Algae Scrubber | Drawbacks

There are a couple of drawbacks to employing an algae scrubber as part of your aquarium filtration system:

  • To put it plainly, algae scrubbers are a hassle to set up. Every sump cabinet is different in terms of size and headroom, so some good ol’ fashioned ingenuity is required in planning your algae scrubber design. And it is not just about the space. Remember that you will also have to find a way to mount the one or two light bulbs close enough to the algae scrubber, without getting them splashed. We do not want a potential fire hazard waiting to happen!
  • An algae scrubber needs a large enough surface area to be efficient. We are looking at a minimum growth area of at least 12 inches wide by 24 inches long (above the waterline in the aquarium sump) to serve a tank of about 150 gallons. Too small a surface area for the algae to grow and the scrubber is virtually useless, serving as little more than a conversation piece when you show the inner workings of your tank to friends and family. Algae scrubbers are best employed in very large systems where there is enough space in the sump cabinet.
  • Algae releases terpenoids and other organic chemicals into the water. In large amounts, such as in an algae scrubber, terpenoids cause the water to turn yellow. Although not dangerous, yellowed water is unsightly and inhibits light intensity or PAR (photosynthetically active radiation) required for most corals and clams. It is necessary to run activated carbon in a system with an algae scrubber to prevent the water from yellowing.

Read More About Marine Aquarium Filtration:

Activated Carbon


Protein Skimmer




Chaetomorpha | Best Macroalgae for the Refugium

Live Rock

Phosphates And Phosphate Adsorbing Media

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