# black algae on rocks



## homerdave (Mar 24, 2010)

I have black algae on my rocks, it does not seem to harm fish and tank is stable, but looks bad. The tank has been set up for 2 years and is well established!

It is a 50 gallon tank with some tinfoil barbs, and tiger barbs. the rocks ( not the gravel) always gets black algae on them. I usually remove the rocks and scrub them to remove algae. 

Is there a way to prevent this?? or a way to get rid of the unsightly algae without removing the rocks??

Thanks,
Dave


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## homerdave (Mar 24, 2010)

P.S. It is only on the top side of the rocks, when I turn the rocks over there is no algae.

Thanks for the help!


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## snail (Aug 6, 2010)

Too many nutrients or too much light are usually the causes of algae problems. If you could tell us a bit more about your tank it would help: size, stocking levels, maintenance schedule and lighting. Also what does the algae look like, is it hairy or slimy?


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## homerdave (Mar 24, 2010)

The algae is slimy. 

I have 3 large (4inches) red tail, tinfoil barbs. 5 tiger barbs, and a black ghost knife fish.

I just use 2 15 watt daylight 18 inch florescent lights, they are on 8 hours a day.

it is a 50 gallon tank, I change 5 gallons (10 percent) of water every week.


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## paronaram (Jul 12, 2008)

Some water movement by circulation pump will reduce that algae as well


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## snail (Aug 6, 2010)

Could be cyanobacteria, I have only seen it in a blue-green color but I've heard it can be black. Does it wipe off easily or do you need to scrub hard? Here is a link on how to deal with cyanobacteria:
Slime Algae - Causes and Cures for Slime Algae


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