Re: Purple slime

Question
I first noticed the purple looking slime today..  I turned a rock over after a saw several brownish looking plants on it.  I tried medication that my local aquarium had said would get removed the plants, which looked to work, then came back.  So I turned the rock over after I told my local aquarium the meds didn't work.  Now I see several spots in my tank with this purple looking slime.  Can anyone tell me what this is?  28 gallon tank, 65 gallon protein skimmer, 130 watt jbj, and one power jet.  Live sand and about 30 lbs of live rock.

Answer
Hi Brian

What you have here is Cyanobacteria.  It is generally caused by high nutrients in the tank.  How long has your tank been set up?  It is fairly common in newly set up tanks and is just one  of the many algae phases you go through.

I would turn the lights off for about 2 days.  Increase skimming and do frequent water changes (ie every week or twice a week).

Don't worry about it.  It will go away eventually.  Also, never dose anything you can't test for.  Dosing chemicals for cyano will only treat the symptoms not the cause.

Kind Regards

Michael