Coralline Flaking off

I've had my tank set up for about 2 years now without problems. The coralline algae on the back is now starting to flake off in chunks. What's up with that. Not that I want the glass covered with algae, but what is causing it to come off?

 

sounds like low Magnesium. Mine will do that if it gets under 1500. I like to keep it at 1800-2k. Sounds high, but I've never had a problem with it. Is algae taking its place?

 

Have you changed your lighting? I started losing it on my glass after I switched from PCs to T5s.

 

how old is your lighting? It's possible you're not getting the cool light you used to due to the age of the bulbs.

 

Lighting is more the answer than low Magnesium. Not sure why people believe certain things but telling someone to run Mag at 1500 sounded incredible to me. Not that you can't but cuttinggras didn't tell you if you were going to raise Mag to only do it about 18 ppm a day. No safe advice was given. Lighting may be more in line here.