id algae

Heyy guys, i need some help identifying what is on my sandbed. I have attached some picture od some sand grains under the digital microscope. Especially the red stuff if anyone knows please help id.

my parameters are in check. i dont know for sure its been many years since i saw cyano. but i think i killed of my diatoms and it seg-wayed into cyano but during that i had a alk swing that ticked off my corals and i think a algae or bacteria problem is why they aren't coming back faster or even...