Quick Question

[ghola5]

Had my first ever tank for about a month now. Two clownfish in it are doing great. Just had my first big cleaning yesterday.
I was just wondering. What exactly is the purple stuff on the live rocks? Is it the good bacteria? Algae? Just wondering what exactly is that stuff.
Anyone shine a light?

 

[dfox]

It is probably coralline algae, if it is kind of hard and flat looking. It is good stuff because it can prevent other kinds of bad algae from growing on the rock. It can be purple, green, red. Mine started growing about 2 weeks after establishing the tank, and the rocks were about 1/2 covered after a month. I've read that you need good calcium levels (400 ppm), low phosphates, and decent (but not incredible) light to grow it.
I'm sure others can add more...

 

[ghola5]

it is now taking over alot of the rock and trying to spread onto the floor of the tank, is it ok if i let it grow on the rocks but clean it from the floor? it just seems like its taking over and some pieces break off and land on something else and start growing there and my tang doesnt seem to eat on it at all. should i just let it take over and do what its doing?

 

[pallan]

you really should not see daily changes in growth from corraline. im thinking you proabbly are having a bout of cynobacteria. not a good thing and does need to be controlled before it gets out of hand. common in new tanks with to many nutrients and possibly a lighting issue.

 

[pallan]

here is a good thread about how to beat red slim algae if that is what you have
google cynobacteria and look for some pictures but from your description im pretty sure thats what you got.
Corraline will not be able to easily be wiped off of rocks or objects it is hard. cyno is soft and velvety look to it.
good luck
https://forums.saltwaterfish.com/t/73002/how-to-rid-your-tank-of-red-slime
and to who wrote this article. i used it to kick mine and still pass it on for ya. great article.