Algae can enter your aquarium from introduced rocks, sand or frags, and when the conditions are right, algae will take advantage and become a nuisance, if left unchecked. Here are some of the most common nuisance algae we see in aquariums and methods to help prevent and treat them.


Diatoms are a major group of microalgae and although they can seem nice to look at when viewed under a microscope they can make your tank look horrible by covering it in brown slime. Very prevalent in new reef tanks, diatoms are often a common nuisance "algae; one of the first to colonize clean, bright surfaces of rocks and coral sand, turning a pristine marine scene into a brown swamp.

Diatoms are a nuisance algae and is common to see when starting up a new aquarium
Cycling a new tank, diatoms are often the first sign of life.

How to beat diatoms

  • A natural method is the use of sailfin or black mollies (brackish fish which can be added to marine systems,) are good at grazing it.
  • Regular maintenance in the form of regular glass cleaning, water changes, and substrate vacuuming. Filter socks, pads and sponges will help catch and remove any that you dislodge into the water, which should then be swapped out for a new filter.
  • GFO or phosphate removal media can help control both phosphate and silicates which helps starve diatoms long term. 


Cyano isn’t algae, and as the name suggests, its a bacteria, but a common nuisance all the same. However, it looks and behaves like algae, being photosynthetic, smothering all the sand, rocks, and glass in red slime. An opportunist, cyanobacteria thrives in fluctuating KH and pH conditions and can even grow in systems with zero nitrate and phosphate or low nutrient aquariums. It starts in the quiet areas of the tank where detritus accumulates and spreads from the substrate upwards.

cyanobacteria, referred to as red slime algae, is a common sight, typically blankets the sand

How to beat Cyanobacteria:

  • Build up a level of nitrate between 5 and 10ppm, but keep phosphate as low as you can.
  • Increase circulation and minimize dead spots with extra wave pumps and fewer rocks.
  • Vacuum the substrate regularly and thin the substrate if necessary. Remove manually with a siphon tube, improve skimming and mechanical filtration, and increase water changes.
  • Algae control products do work, but are more of a band-aid to underlying issues, resulting in the red slime coming back.

Green Hair Algae

Green hair algae thrives in bright light and high phosphate levels. It prefers bare rock surfaces, ideally those like natural reef plates or reef bones which are leaching phosphate from previous die-off. In severe cases, it grows long and stretches across the tank like green spider webs, but it can also be short like turf.

green hair algae tends to grow on liverock

How to beat Green Hair Algae

  • Unlike Diatoms and Cyano, hair algae has a nutrition value which some invertebrates and fish will graze on. A diverse clean up crew of hermit crabs, assorted snails, urchins or a sea hare, can put some work in on ridding the algae.
  • For fish, use Zebrasoma or Ctenochaetus tangs, rabbitfish, or algae blennies. Be sure that your aquarium size is sufficient enough to house an appropriate amount of livestock, if using this method.
  • Phosphate control methods can be used to starve it, or introducing competing algae to the system via an algae scrubber or macroalgae refugium would also help to rid the system of spare nutrients, and fight the nuisance algae.

Bubble Algae

Bubble algae is introduced on the base of corals or live rock and tends to manifest itself as the tank ages. If left, it can smother all the rocks in the tank, block pump inlets and can even kill corals. A common characteristic of this algae is that it also traps detritus between it's bubbles which fuels even more algae growth.

bubble algae can grow into large colonies on is common on rock structures where there is good lighting and insufficient water flow

How to beat Bubble Algae:

  • Crushing the bubbles is not recommended as some sources believe it releases spores to the tank, causing more to spring up. Emerald crabs (Mithraculus sculptus) should be considered and are a natural bubble algae specialists. They will help tackle and prevent future bubble algae outbreaks. For severe infestations, multiple crabs may be needed.
  • Naso and vlamingi tangs have been observed eating the algae, but seasoned hobbyists know that fish "personalities" will vary. These tangs also require a large aquarium they can grow into.
  • Brightwell Razor Systemic Cleaner has also proven effective on bubble algae. Brightwell Razor cleans the surface of the aquascape, making it harder for bubble algae to attach. Bubble algae begins to detach from surfaces and can be scooped, siphoned, or filtered out.
  • Manual removal, by taking the rock out and prying the colonies off of rock. Then rinsing the rock in new saltwater before placing back into the aquarium.


Macroalgae is another name for seaweed, and many forms grow in the marine aquarium. We utilize some like Chaetomorpha or Caulerpa to help tackle other nuisance algae, though they can be invasive if released into non-native waters. Macroalgae is also encouraged in seahorse aquariums, but in reef tanks, it does compete with corals in space, light, and nutrients. Some sources also believe it can release chemicals which stunt coral growth. So keeping a reef free of macroalgae growth in the main display, is common. 

close up photo of macro algae

How to beat Macroalgae

  • Harder to come by, but live rock taken from the ocean should not be used, as it often carries macroalgae with it.
  • Rabbitfish, surgeonfish, angelfish or a combination of these fish will constantly graze the rockwork and help to prevent it from growing.
  • Manual removal by hand by taking out infested rocks, scraping off the algae, and rinsing the rocks in a bucket of tank water before placing it back in the tank.
  • Urchins are great at mowing down macroalgae too, cutting through to the base where the algae attaches to the rock. 

Calcareous Algae

Pink and purple coralline algae are loved by some and loathed by others. It likes the same conditions as corals, so purple circles appearing on pumps and the tank glass can be taken as a good sign that your parameters are right. Just note that too much calcareous algae will use up alkalinity, calcium, and magnesium, competing with corals, causing you to use more supplements.

common, but not usually thought of as a nuisance until it begins to affect the flow of aquarium circulation

How to beat Calcareous Algae

  • When on growing on glass calcareous algae can be scraped off with an algae magnet equipped with a metal blade, like the Flipper Float Algae Scraper. Otherwise, a razor blade can be used very carefully to not scratch the glass nor cut into the silicone holding the tank together.
  • Urchins are one of the few invertebrates that can eat it, along with pest Asterina starfish, but Asterina stars can become problematic in your reef tank.
  • When growing on pumps, a soak in a cleaning solution, like Sicce Pump Clean, for a few hours, followed by scrubbing with a soft bristle brush can clear out calcareous obstruction. A distilled vinegar-water (1:1) solution soak can be used too.


Easily confused between diatoms and cyanobacteria, dinoflagellates tend to be on the browner side in color. They aren't an algae, but a small marine plankton, common nuisance that forms a mat on sand and rock producing slime-like brown strings and trapped air bubbles. Dinoflagellates are a menace when they get out of control and can have many hobbyists scrambling to find ways to get rid of them.

Nuisance Algae

How to beat Dinoflagellates:

  • Manual removal by through water changes and siphoning sand lowers the infestation.
  • Nutrient control helps prevent an outbreak so be sure to maintain water parameters accordingly. Test nitrates and phosphates and if undetectable, the imbalance may be the cause.
  • Dosing nitrogen and phosphorus in low nutrient systems along with liquid carbon dosing has been reported to help by feeding beneficial bacteria to help regain balance of the nutrients in the tank.
  • Since they are photosynthetic, blacking out your tank for a few days has also been reported as an effective means of control.

Final Thoughts

Keep in mind that algae occurs naturally within home aquaria, but without maintaining a proper balance of your nutrients, it can get out of control, quickly. So, be sure to keep up with your tank maintenance, have a diverse clean up crew, and observe your aquarium each day as preventative measures.