How to Get Rid of Algae in a Saltwater Aquarium

Regular maintenance will control algae growth.
Regular maintenance will control algae growth. (Image: Krakatuk/iStock/Getty Images)

Although some algae growth is a good sign that your aquarium is self-sustaining, too much algae growth can become both unsightly and unhealthy for the aquarium. Excess algae growth can decrease water quality and cause fluctuations with oxygen, carbon dioxide, nitrate, phosphate, pH, hardness and alkalinity levels in the tank. You want to get rid of excess algae with regular aquarium maintenance, algae-eating creatures and basic saltwater aquarium care.

Types of Saltwater Algae

Diatoms, also known as brown algae, can form a slimy, golden-brown coating on the aquarium glass and solid objects within the tank. Diatoms bloom in poor water conditions and can be quite common in newly set up aquariums.

Red algae has a distinctive pink, bushlike structure. Red algae is considered good algae that grows in good water conditions, bright light and even water with high calcium levels. Red algae is rarely problematic as it grows slowly. Red algae tends to grow on live rock and rarely floats in the water.

Green algae, also known as hair algae, is similar to red algae, but it can grow quickly if it's not pruned back.

Cyanobacteria is also known as blue-green algae, but it's actually a bacteria. Cyanobacteria is a dense slime that can be blue-green, red or black. When removed from the water, it has a musty odor. Cyanobacteria tends to flourish in poor water conditions and in aquariums with little water movement. it can be hard to maintain so prevention is key.

Dinoflagellates are unicellular algae that comes in a variety of colors. This type of algae is toxic to a saltwater aquarium, so you want to check for them regularly. Prevention is the key because dinoflagellates are hard to remove. Frequent water changes and stable carbon levels will keep them in check.

Bubble algae is green and shaped like small bubbles. This type of algae can be a pain to remove because if the bubbles are popped, thousands of spores are released into the water.

Control The Algae

The best way to get rid of algae is to prevent it.

  • Ensure proper lighting with a 8 to 10 hour photoperiod. Some slimy algae types, like diatoms, thrive in poorly lit aquariums, so a proper photoperiod will help reduce these types of algae.
  • High levels of nitrate and phosphate can prompt algae growth, so check your water conditions regularly and perform regular water maintenance. Cyanobacteria is one type of algae that will bloom rapidly with high nitrate and phosphate levels.
  • Use a protein skimmer to filter decaying matter before it is broken down into nitrate and phosphate. This is easily one of the most important pieces of equipment in maintaining a saltwater aquarium.
  • Place plants in the filter to absorb the nitrates, starving the algae. These types of refugiums will enhance the water quality by maintaining pH levels and reducing nitrate levels.
  • Add a UV sterilizer to your setup. It will kill waterborne algae that cause diatom and green algae growth, but it will not affect algae that grow on solid objects.
  • Use cured live rock to in the aquarium. The cured live rock will absorb excess nitrates and phosphates and keep levels in check.
  • Do not overfeed the fish and creatures. Uneaten food will decay and increase nitrate and phosphate levels.
  • Keep the number of fish you have in the tank appropriate to the size of the tank. The general rule of thumb is at least one-half inch of expected adult length per gallon of water.

Regular Routine Maintenance

Regular tank maintenance is one of the most important methods to keeping a saltwater aquarium clean and keeping algae at bay.

Siphon about 20 percent of the water throughout the month to ensure that there isn't a buildup of phosphates and nitrates in the water. To reduce stress on the aquarium, remove 5 percent a week or 10 percent twice a month. Each time you perform a partial water change, clean the filter to remove any algae buildup on the equipment.

When refilling the water, make sure you do not add freshly mixed saltwater. Mix the water the day before. Use a sea salt mix that contains higher calcium and alkalinity levels.

The protein skimmer will help limit excess vitamins and minerals in the water that inhibit algae growth, so you want to ensure that it is working efficiently. Check the skimmer regularly and clean it at least twice a month.

Regularly scrape algae from the aquarium glass with a scraper.

Saltwater Algae-Eating Creatures

Add fish and other creatures who feed on algae to help keep excess algae growth down but will not eradicate unwanted algae in your aquarium.

Snails There are many types of saltwater snails, but a few algae-eating snails include turbo snails, astraea snails, turban snails, nerite snails and margarita snails.

  • Turbo snails will scour the entire aquarium, eating mostly green hair algae.
  • Astraea snails will travel across the entire aquarium, eating mostly cyanobacteria, green and brown film algae.
  • Turban snails, also known as trochus snails, will clean the entire aquarium, including the glass. They will eat mostly green hair algae, slime algae, green algae, cyanobacteria and diatoms.
  • Nerite snails typically clean off rocks and glass, eating cyanobacteria and green algae. Nerite snails are perfect against algae film on the glass.
  • Margarita snails will clean the hair algae, cyanobacteria and diatoms from the rocks and sand.

Fish Most species of tangs will nibble on green algae. Blennies will consume red and green algae, but generally won't harm large decorative varieties. * Dwarf angelfish will feed on green algae, but need supplemental feeding to complete their diet.

Other Marine Creatures There are various crab species that will eat red and green algae. Hermit crabs will eat just about anything they can catch, but they also will eat various types of algae. Sea hares consume mostly algae as a daily diet. Various sea urchin species will feed on red and green algae. Be careful of the species, as some will damage coral and polyps.

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