FTC Disclosure: Fishpondinfo contains affiliate links, and, if you click on such a link and make a purchase, and I meet their minimal requirements, then I will be compensated.

Home Animal Index Fish Index Pond Index Master Index Contact
Pond Newsletter Message
Board Pond Book Calculator
Donate Interactive Fishpondinfo Stores Pond
Showcase Guestbook

Aquarium and Pond Algae Types

Last Updated: 2/21/14

Here is the proof that even my 1800 pond was pea soup green with suspended algae when it was new and about a year old on 4/12/98.

Green Surface Algae
Suspended Algae
Hair Algae
Blue-Green Algae
Brown Algae

This is a page of descriptions of algae and not how to deal with them which is covered on other of the algae pages.

I have combined the information on algae types from my former aquarium and pond algae pages into this one page since there are so many similarities between aquariums and ponds. For more on algae control in aquariums, see my aquarium algae index. For more on algae control in ponds, see my pond algae index.

There is a nice site with photos of various algae in aquariums at Aquaticscape.com. It has very good photos and short descriptions.

Green Surface Algae


Green surface algae is the most common algae found in aquariums. It creates a thin layer of hard-to-remove, dark green algae. Algae-eating fish and snails prefer this type of algae. It can be physically removed but can be difficult. It usually needs to be scraped off. Surface algae is usually only a problem in that people view it as unsightly although sometimes it may block light to live plants if it grows on their leaves.


Green surface algae is the best kind of algae to have in a pond. It is found on any surface and is very short. This short green algae is a vital food for snails, tadpoles, fish, fry, aquatic insects, and other aquatic creatures. It also acts like a higher plant, helping to filter out nutrients in the water. Brush algae is a less advantageous type up surface algae with longer filaments that suffocate plants. Rainbow shrimp are supposed to eat brush algae but cannot survive below the 60's degrees F (see my shrimp page for more information.).

Suspended Algae


If the water itself is green, there is suspended algae. This should not occur in well-filtered aquariums. If it does occur, water changes will reduce the effects. It most often occurs if there are too many fish, too much food added, or excess light. Correcting those things should prevent a reoccurrence. UV sterilizers can be added to the setup if needed. See my pond algae page for more information on suspended algae and controlling it. In ponds, daphnia can also be added. The wood shrimp eats suspended algae in aquaria.

In the winter of 2009, I had to keep six feeder goldfish in a 10 gallon until spring. At first, the tank had a massive brown algae (diatoms) bloom that lasted for months. Then, sunlight started to hit the tank. The result was no more diatoms but a very strong suspended algae bloom. Since the tank was well aerated, I did not care much since it was not harming the fish. I decided for visitors on Easter though, the tank should be clear so I put in a dose of AlgaeFix by Aquarium Pharmaceuticals for ponds. I do NOT recommend algaecides as a common treatment but rare use should be fine. I only use it regularly as a preventative in an ornamental pond on the porch that has no life in it.
Suspended algae bloom in the 10 gallon gallon tank on 4/10/09.
Clear tank after algaecide on 4/12/09.


Suspended algas come in hundreds of different species. They color the water green (or sometimes brown) preventing ponders from viewing their fish. At the same time, they provide food for microscopic animals and plants that larger animals eat down the food chain. A goldfish may eat a mayfly that ate a cyclops that ate a paramecium that ate algae, etc. Thus, some suspended algae is necessary for a complete ecosystem. Obviously, if you only want large fish and are feeding them, then you may not want or need an ecosystem. Others, like myself, strive for as natural a pond as possible. Fry will grow the best in waters with some suspended algae which provide food for the microorganisms that they need.

Hair Algae


Hair algae is very common in ponds but less so in aquariums. If the algae is in long strands, then it is hair algae. Few animals will eat it. It is best to physically remove it by whirling it around fingers or sticks. Hair algae may be called brush algae, filamentous algae, or string algae.

Most aquarists now recommend American flag fish and rosy barbs for eating hair algae in aquariums. Some cherry barbs and maybe other barbs may eat some too. Another person says that golden nugget plecos eat hair algae.

My twenty gallon tank became infested with hair algae in March of 2001. I think it came in with some plants I moved from the pond. I tried a real SAE and a few new rainbow shrimp. I had a false SAE and a few rainbow shrimp that were not helping. I also added barley straw to a mesh bag in the filter box. None of this seemed to help. Physical removal did the most. The poor fish kept getting stuck in the hair algae which grew well under strong lighting while the plants could not compete (I do not have carbon dioxide injection). After the goldfish in my 50 gallon tank all died from tuberculosis in April of 2001, I re-setup that tank from scratch, cycled it with other fish, and finally moved the 20 gallon fish and shrimp to the 50 gallon tank on 6/16/01. Then, I bleached out the 20 gallon tank to kill the algae. I tore down the tank because I was moving fish, not because of the algae but hopefully, the hair algae would not come back! [Update: By 1/23/02, the newly setup 50 gallon tank was full of live plants AND hair algae. The real SAE did not touch it nor did the white cloud mountain minnows (who got stuck in it), panda cories, otocinclus, or rainbow shrimp. I thought I would have to try some flag fish or rosy barbs myself soon! Later Update: I did add two rosy barbs then, and the hair algae vanished after many months after they spawned in it.] Update 4/21/06: The two rosy barbs begat 30-some. There is not a strand of hair algae to be found but the java moss grows really well.


Hair algae is a slimy, bright green, filamentous algae that grows up to a few feet in length. It typically is about an inch long but tends to grow up to a few feet long in moving water. Hair algae is also called string algae and filamentous algae. It clings to the sides of the pond, pots, and any other surfaces. It can smother plants and clog filters. On the up side, it removes nutrients from the water and thus reduces the concentration of suspended algae so that you can see through the water better. Hair algae seems to do best in the winter in my ponds and likes moving water. It is unaffected by UV sterilizers because it does not pass through them. It is best to physically remove it by whirling it around fingers or sticks.

String algae does best in late winter when it provides an additional source of food for animals in the pond. Normally, fish would not eat it in the summer but in the late winter, not much else is available. The hair algae also, being a plant, provides some filtration of the water, helping to keep the rest of the pond clearer. When the pond warms up in spring, the hair algae usually dies back and the suspended algae begins to grow as well as the higher plants. If hair algae appears to take over the pond in the late winter, there is no need to panic. Simply physically remove any that interferes with filters, etc. and wait it out.

Blue-Green Algae


Blue-green algae (BGA) are not true algae. They are cyanobacteria. If objects in the tank are coated with thick sheets of slimy, bright-greenish blue algae, it may be blue-green algae. Sometimes the color almost seems to fluoresce. It commonly grows in tanks with too many nutrients. Scrubbing it off and then doing a 50% water change should help. Do frequent large water changes until it goes away. Reduce the quantity of fish or food added. The treatment with antibiotics may kill some or all of the blue-green algae but could also kill good bacteria. When the treatment is ended, the blue-green algae may return. This stuff is nasty! It is a beautiful green but slimy and coats everything once it takes over.

My forty gallon tank became infested with this algae in March of 2001. Natural light was hitting the tank in the spring so despite 50% weekly water changes and gravel vacuuming, it took over. I tried the treatment of erythromycin (I used Maracyn by Mardel Products). After treatment was done (five days), the blue-green algae was definitely knocked back but it was not all gone. By the following week, it was completely dead. I get occasional spots in my 40 and 50 gallon tanks but as long as I remove the little spots, it does not seem to spread. After a while, it does come back bad again, and I have to use the Maracyn again.

The following animals are supposed to eat blue-green algae but I do not know if they work: American flag fish (Jordanella floridae), butterfly goddeid (Ameca splendens), Procatopus, and red ramshorn snails. I do not know anything about the last three animals nor have I ever seen them. The red ramshorns are sometimes sold by Frank at Frank's Aquarium.


Cyanobacteria are less common in ornamental ponds than aquariums but sometimes do occur, mostly in stagnant ponds of any size. In the summer of 2003, my 50 gallon lotus tub pond became covered with a bright green slime. The lotus had died that year so the pond had almost no plants in it and no animals and yet moderate sunlight. The water was not moving and stagnant. The green slime was blue-green algae, a cyanobacteria. It would fall apart into sheets when it rained or the water was disturbed. I added a small pond pump to agitate the water, and the algae was totally gone in a few weeks. If an algae sheet on the surface falls apart in the rain, it is probably blue-green algae. It is simple to get rid of it by surface agitation. Big ponds can use fountains or aerators. For small ponds, any water movement will work. For this reason, blue-green algae is not normally encountered by us high-tech ponders.

Brown Algae


Brown algae are actually diatoms and not true algae. They coat ornaments, real and fake plants, glass, and gravel with a thin, dark brown layer. Brown algae prefer low light levels. They commonly grow in new tanks or those with low levels of light. Increasing the intensity or quantity of lights may decrease the growth of brown algae but in turn will increase the growth of other algae. Brown algae is easy to physically remove with an algae pad as it does not adhere as strongly as green algae. While some snails and algae-eating fish will inadvertently eat some brown algae, most algae-eating fish prefer green algae and will only eat brown algae if they have no alternative food source. Plecostomus and otocinclus are the most likely fish to eat it.

This photo taken on 3/7/09 shows diatoms (brown algae) growing on the bottom glass of my 10 gallon tank which was temporarily holding goldfish:


Brown algae is less common in ponds because outdoors, there is plenty of sunlight, and brown algae like low light levels. It may grow in darker areas of the pond.

Pet Link Banner Exchange:

Go to the main plant page (full index).
Go to the aquarium algae index.
Go to the pond algae index.
Go to the aquarium plant index.
Go to the pond plant index.
See the master index for the plant pages (quick index).

Like Fishpondinfo
on Facebook Follow Fishpondinfo on

E-mail Robyn

Copyright © 1997-2023 Robyn Rhudy

Follow Fishpondinfo on
You Tube Follow Fishpondinfo on Instagram