What is going on?

[skinnywater66]

I had what I though was red cyno covering the sand and some rocks that I have had for awhile. After doing a couple small water changes (10%) two days apart I woke up this morning and the red mat on the sand changed to a green color and my skimmer is going crazy. When my lights came on the water has a pink tint to it and there are so many pieces of this green stuff that used to be red the day before floating around. Here is a pic of what is on the sand bed that was red and turned green overnight.

 

[Dan_P]

I had what I though was red cyno covering the sand and some rocks that I have had for awhile. After doing a couple small water changes (10%) two days apart I woke up this morning and the red mat on the sand changed to a green color and my skimmer is going crazy. When my lights came on the water has a pink tint to it and there are so many pieces of this green stuff that used to be red the day before floating around. Here is a pic of what is on the sand bed that was red and turned green overnight.

@taricha?

 

[EeyoreIsMySpiritAnimal]

I had what I though was red cyno covering the sand and some rocks that I have had for awhile. After doing a couple small water changes (10%) two days apart I woke up this morning and the red mat on the sand changed to a green color and my skimmer is going crazy. When my lights came on the water has a pink tint to it and there are so many pieces of this green stuff that used to be red the day before floating around. Here is a pic of what is on the sand bed that was red and turned green overnight.

Did you add anything to the tank to combat the algae?

 

[skinnywater66]

No. Nothing was added.

 

[taricha]

pretty clear that what happened is that a bunch of cyano died. It loses its pink phycoerythrin pigment into the water and the left behind tissues stay green (chlorophyll not water-soluble)
The mystery is how you got a bunch of cyano to mass die-off. I have no good guesses.