HELP!! Black Slim Algae

[lions den]

I set up a 20 gal reef about 3 months ago and I have have a bad problem with this black looking slim algae. It is spreading very rapidly and I cant figure out how to get rid of it. Any ideas?

 

[moray345]

how long are your lights on evry day had mine on for 12 hours evry day then cut it to 6 and built up evry week to only 8 hours and the cyano left immediately

 

[lions den]

They are alos on for about 12 hours a day. I will cut it down and see what happens. Thanks for the input

 

[solonfairy]

increase waterflow/oxygenation of the tank
then do whatever it takes to keep no3 and po4 to a minimum
in the meantime, siphon out what you can and do more frequent large water changes
b/w all of that, you wont have the problem anymore.