QUICK growing algae/bacteria ID, help with underlying cause please

Realamerican13 · Nov 6, 2019

I have had a 25 lagoon up for about 6 months, over the past week I’ve had a very quick growing algae or bacteria which started to cover my rock then moved to the sand. It grows pretty quickly when lights go on eventually become a long stringy red algae on rocks, started covering some corals (GSP AND ZOAS especially). Then over past few days has spread to sand bed. Tank parameters from most recent test are salinity 1.025, alk 8.5, ph 8.1, nitrate 20, phosphate measured with Hannah ULR .06 (up from zero 2 weeks prior), calcium 475, mag 1520. I use rodi water, tank is equipped with aqamai kps powerhead, stock mighty jet return pump, IM skimmer and media reactor running biopellets, 2 nano chemipire packets and filter floss. I was doing weekly 5 gallonwater changes but tried stretching it to 2 weeks which is when the problem started. Here are some pics of what I’m working with, I did 2 runs of chemiclean which did not rid tank of what I think is cyano but I’m not experienced enough to be sure (first tank). So I just did 2nd water change after second run of chemiclean, put in new chemipure packets and just started a 3 day blackout. Anyone think this is dynos or red turf algae? Sand bed is clean in the morning but has a lot of red algae or bacteria on it after just a few hours. Also recently added a 2nd ai prime, maybe need to dial back lighting schedule after blackout. I have some lps, a RBTA, and a few zoas along with 2 clowns, firefish, sand sifting goby, and possum wrasse.