Fuzz growing on live rock - help to ID

[rmsmith]

Hi, looking for a little help to identify this fuzz that is growing on my life rock. Tank is approximately 140 gallons, just over a year old, but most of the rock and fish were transferred from my previous tank of six years. No additions or subtraction’s to the tank in over six months, try and keep it fairly low maintenance.
I’ve tried to scrape it off with a toothbrush, and it doesn’t seem to want to come off. The rocks with a good covering of Coraline algae don’t seem to have the same issue.

 

[FishTrader]

I can't tell by the pictures, Google "diatoms" and see if it's a match.

 

[rmsmith]

Thanks. That could be the issue. Some of the rock I added was base rock from BRS so could be a source of the silica for diatoms to feed on?? Tried more pictures with more white light.

 

[I never finish anythi]

Did you ever get to the bottom of this algae? I have a very similar thing growing on one of my rocks . Almost looks like ash . Looks dirty

 

[rmsmith]

Hi, not really. The problem has now morphed into a brown hair algae bloom. Doing 15% water changes every 2 weeks, added GFO and now changing out my RODI membranes to see if that was the source. I didn't realize I haven't changed in over a year. All the livestock are healthy so trying not to make drastic changes.