Please help identify this? Pics.

In my 29 gal nano with my sea horses. I was just about to do my monthly partial water change and turned off all my pumps and filtration. All of a sudden in a matter of minutes the purple algae turned into a rust colour??? I have never seen this before. I quickly sucked it all up and replaced the water and turned on the filters. All looks good again. But what what/is this some kind of diatom?






Thanks

 

cyano! what kind of water are you using?

 

Yes I understand that I have cyano and yes I try to use RO water as much as possible, but sometimes I get lazy and use tap water, although I have heard that our water is glacial. (I live in Central Interior of BC Canada). My question is why did the Cyano change colours within a matter of seconds as soon as I turned off the filters and pumps? It was just very creepy!

 

I had this happen a couple times in the past, I think it must have to do with a change in pH or alk. It's almost a fluorescent orange, glowing and then it goes away.