Freshwater Algae

Freshwater Algae Guide

Some algae is normal in a healthy aquarium. When it becomes excessive, identify the type, remove what you can, and correct the conditions allowing it to grow.

Don't panic — and don't completely tear down the aquarium.

Start by identifying what the algae looks like. Reduce excess light and food, manually remove as much as possible, and then use the appropriate algae eater or treatment if needed.

Long Green Strands Hair Algae
Blue-Green Slime Cyanobacteria
Dark Fuzzy Tufts Black Beard Algae
Brown Dusty Coating Diatoms
Hard Green Dots Green Spot / Film Algae
Green Cloudy Water Free-Floating Algae

Hair Algae

Long green threads or fuzzy green growth

Hair algae usually appears as soft green strands growing from plants, rocks, wood or decorations. It can become long enough to wave in the current.

Natural Control
  • Pull or twist out as much as possible by hand.
  • Reduce an overly long lighting period.
  • Avoid overfeeding.
  • Siamese Algae Eaters can be very effective.
  • Appropriate shrimp and snails can help with softer growth.
Treatment Options
  • Perform regular water changes.
  • Remove accumulated organic waste.
  • Improve mechanical filtration.
  • For persistent algae, consider Fritz Algae Clean Out.
Wet Pets Recommendations: Siamese Algae Eater · Panda Garra · Fritz Algae Clean Out · Seachem Purigen

Cyanobacteria — Blue-Green Slime

Slimy blue-green sheets that peel away easily

Cyanobacteria is actually bacteria rather than true algae. It often forms smooth, slimy sheets over substrate, plants or decorations and may have a noticeable odor.

Natural Control
  • Siphon out as much as possible.
  • Increase circulation in dead spots.
  • Remove trapped waste from the substrate.
  • Reduce excessive lighting.
  • Keep up with regular water changes.
Treatment Option
  • Fish and snails usually will not solve cyanobacteria.
  • Correct circulation and excess waste first.
  • For persistent outbreaks, Fritz Slime Out can be used specifically for cyanobacteria.
Wet Pets Recommendations: Fritz Slime Out · Seachem Purigen · API Freshwater Master Test Kit

Black Beard Algae — BBA

Short dark gray, black or reddish fuzzy tufts

Black beard algae forms tough, short fuzzy patches, often along plant leaf edges, driftwood, rocks and equipment. It can be one of the more stubborn freshwater algae problems.

Natural Control
  • Remove heavily covered leaves.
  • Scrub removable rocks and decorations.
  • Reduce excess light and organic waste.
  • Siamese Algae Eaters are one of the better fish for BBA.
Treatment Options
  • Keep lighting and fertilization consistent.
  • Avoid large swings in CO₂ if CO₂ is being used.
  • Manual removal should be the first step.
  • Fritz Algae Clean Out can be considered for persistent algae growth.
Wet Pets Recommendations: Siamese Algae Eater · Fritz Algae Clean Out · Seachem Purigen

Brown Algae — Diatoms

Soft brown or dusty coating on surfaces

Diatoms commonly appear as a brown dusty film on the glass, substrate, rocks and decorations. They are especially common in newer aquariums.

Natural Control
  • Wipe the glass and siphon the substrate.
  • Give a newer aquarium time to mature.
  • Nerite snails are excellent surface grazers.
  • Otocinclus can help in established peaceful aquariums.
Usually No Chemical Is Needed
  • Maintain normal water changes.
  • Clean mechanical filtration regularly.
  • Avoid overfeeding.
  • Diatoms often decrease naturally as the aquarium matures.
Wet Pets Recommendations: Tiger Nerite Snail · Zebra Nerite Snail · Otocinclus

Green Spot & Green Film Algae

Green coating or hard green dots on glass and decorations

Green film is usually a soft coating on glass and hard surfaces. Green spot algae forms harder individual green dots that can be more difficult to scrape away.

Natural Control
  • Clean the viewing glass regularly.
  • Nerite snails are excellent glass and rock grazers.
  • Bristlenose Plecos graze many aquarium surfaces.
  • Otocinclus are useful for softer algae and biofilm.
Reduce Regrowth
  • Avoid excessive lighting duration.
  • Keep up with normal aquarium maintenance.
  • Remove excess food and accumulated waste.
  • Fritz Algae Clean Out can help when true algae becomes excessive.
Wet Pets Recommendations: Batman Nerite Snail · Otocinclus · Bristlenose Pleco · Fritz Algae Clean Out

Green Water

The water itself looks green or pea-soup colored

Green water is different from algae growing on surfaces. It is caused by microscopic algae suspended throughout the water column.

Natural Control
  • Keep the aquarium away from direct sunlight.
  • Shorten an excessively long lighting period.
  • Reduce overfeeding and excess nutrients.
  • Perform normal water changes and filter maintenance.
Treatment Options
  • Improve mechanical filtration.
  • UV clarification can help with free-floating algae.
  • Fritz Algae Clean Out can be used for applicable algae outbreaks.
  • Correct lighting and nutrient issues to reduce recurrence.
Wet Pets Recommendation: Fritz Algae Clean Out

Which Algae Eater?

Different algae eaters are better at different jobs.

Hair / BBA
Siamese Algae Eater
Glass / Rocks
Nerite Snails
Soft Algae
Otocinclus
General Grazing
Bristlenose / Panda Garra
When Natural Control Isn't Enough

Chemical treatments can be useful, but they work best after excess algae has been manually removed and the underlying lighting, feeding or maintenance problem has been corrected.

Fritz Algae Clean Out — for applicable true algae problems.

Fritz Slime Out — specifically for cyanobacteria / blue-green slime.

Heavy algae growth? Check the aquarium first. Test nitrate and make sure ammonia and nitrite are zero. Look at how much food is entering the aquarium, how long the lights are running, whether the tank receives sunlight, and whether waste is accumulating in the substrate or filter.

API Freshwater Master Test Kit
Filtration Can Help — But Fix the Cause Too.

Removing accumulated organic waste can help reduce the nutrients available to nuisance algae. Purigen can help remove organic waste from the water, while phosphate-removing media can be useful when phosphate is actually excessive.

Seachem Purigen  ·  Seachem PhosGuard

When using an algae treatment: Always follow the product label for dosage, treatment interval and water-change instructions. Do not increase the dose because the algae is severe. Remove as much algae as practical before treatment and maintain good aquarium aeration.
Don't buy an animal only because you have algae. Make sure any Siamese Algae Eater, Pleco, Otocinclus, Garra, snail or shrimp is appropriate for your aquarium size and compatible with the fish already in the tank. Algae eaters are living animals that still require proper care and supplemental food.

The Simple Wet Pets Algae Plan

1
Identify It Know which algae you're dealing with.
2
Remove It Manually remove as much as practical.
3
Correct the Cause Check light, feeding, waste and water quality.
4
Add Help Use the appropriate grazer or treatment if needed.

A small amount of algae is normal and does not mean an aquarium is unhealthy. The goal is control, not necessarily an aquarium with zero algae. If you aren't sure what type you have, take a clear photo and bring it to Wet Pets Aquatics. Identifying the algae correctly makes choosing the right solution much easier.