Agree with that. the cyano and "It’s slimey, stringy, and it comes off the rocks easy" tells me its most likely dinos.
If this is accurate, or as accurate as we can get with API, Need to know some additional information. Please tell us what your tanks age is, if live rock was initially used or if it was dry rock, what your stocking level is, and what type of lights and lighting schedule you are using. It appears in your first picture that there is an abundance of hair algae on your back glass. My initial reaction to all of this is that your tank is having stability issues. I'm not that concerned with your nitrates as many successful reefers run at a higher NO3 myself included. If your Po4 is truly .03 that is to low. It sounds like perhaps you could use a good thorough tank cleaning ( algae removal), and then to start on a strict maintenance schedule to provide some stability. This would include more frequent and better testing, manual removal of the dinos, and water changes only when appropriate.
See if you can grab a salifert phosphate test kit and do it with that. Three is awfully high for a reef tank.
I use 3 of these on my tank and the only corals I have are softies and they are all doing fine and growing!
Water temp: 77-78
Unfortunately no - I still need to do a lot of learning for "pest" algae ID; I do think a microscope would be a good idea for this though.
