Red stringy algae with smell

[Logans54611]

I don’t know what this is or how to get rid of it. I’m very new to this but I just changed out 7% ish of the water and lightly siphoned the sand bed. I’ve been throu the ugly stage and the mushroom and other coral are doing great. Salinity and ph are sitting at .025 and abt 8.1 I’m pretty sure the green algae is ok so not worried it didn’t smell when the green showed up but the red showed up now it smells kinda weird. Tried to take pictures but it’s stringy thin and carpeting small areas

 

[Reefing_addiction]

Nitrates phosphates?
Filtration?


Ugly stages happen more than once

How old is the tank

Possible cyano
Which is from an imbalance in tank chemistry (usually between nitrates and phosphates I believe)

 

[Logans54611]

I’ve been using small doses of reef code a and b. I’ve got a 3 stage filter that hangs off the back. It’s abt 9 months old