Trying to identify...

[Dchartley]

...what this is and if it is harmful or not.

It started growing a few months ago and it's only on one rock.

Thx for any help...

 

[florida reef]

It looks similar to a type of algae that was growing on some live rock in my dad's tank and since it randomly started growing in your tank I would assume it is algae. Not sure if it's harmful or not, but it's unsightly so I removed it. I would just follow the standard protocol for algae, water changes and good water quality.

 

[bct15]

My brother inlaw had that in his tank, I don't remember what it is called but is most definitely a type if algae...it can get out if hand really fast if not kept in check. I personally thought it looked kind of cool, but would not want them all over my tank

 

[Dchartley]

Thanks for the info. I was guessing some type of algae but wanted other opinions. My wife likes them, and since they are only on one rock I've left them alone. If they start spreading I'll probably remove them.