What the heck is this gray algae?

This stuff is forming on my rock now and I have no clue what it is or why it's there. It's this gray fuzzy looking algae that is all over my LR. It has this soft suede look to it. I am hoping it's not another fungal outbreak or something like that. The tank has no livestock in it, only LR and LS, it's my 150G. Sorry that pic isn't tack sharp, the glass is pretty thick. Any ideas? Thanks guys!

 

It sounds like Cyano - any chance its becoming black?

 

Nope, not black, and it's not stringy. It's just a very pale grey. I wonder if my kalk has gone bad. It looks like fuzzy stuff, not typical cyano consistancy. It actually started forming after I dosed with kalk to raise my pH and Ca.

 

calcium percipitation?

(ack - somehow posted before I was done typing, new forum for me....rookie mistake !)

Was the kalk made up and let to sit for days? Kalk over time will reduce your PH.

I recall something about Kalk and carbon dioxide when it sits around, but I can't recall if it will result in sediment in your tank. Sounds liek all you need to do is suck that crap out of your tank. If I have time later I will do a search and see what i can come up with.

 

Calcium will precipitate in a funny way. I have recently seen it once. When people say "your tank will snow" it means your tank will snow. It's actually pretty funny to see because the calcium in the tank will spray out like snow flakes before they finally dissolve. When I dose my tank with kalk, I just get a small container of water with lid, get a tsp of kalk and shake it up hard in the container until it dissolves fully. Then I slowly dump it into the tank evenly. I never let kalk sit. Kalk is actually limewater and will raise your pH. In many systems, it is used as the counter to low pH in calcium reactors.
I scrubbed the stuff off the rocks a couple weeks and it grew back. I didn't add kalk after the last scrub, so I'm not sure if it's from adding the kalk or maybe an effect of the kalk.

 

Nobody else has any ideas? I'm afraid to add any fish into this tank with this stuff in there, I don't want to risk them dieing. The only thing I could find that is gray algae is staghorn algae, but that is FW algae. I'm completely lost on this.