Stringy slime algae problem

[chef_pinky]

So I’m having what Im calling a stringy slime algae issue, pictures attached.
Here are my parameters and lighting cycle, tank is a 150 cube (24” deep) with 2 hydra 26 HD’s 12” above the water. Testing done with Red Sea test kits, tested multiple times to insure accuracy because I honestly didn’t believe these numbers to be true the first go around. Anyone have any suggestions on how to kick it without chemical use?
Salinity - 1.025
Ph - 8.4
Nitrites - 0
Ammonia - 0
Nitrates - 0
Calcium - 440
Magnesium - 1400 (slightly high)
Phosphates - 0
Alkalinity - 3.5
Temp: 78
Salt - Red Sea coral pro
Water - 0 tds ro/di water. 15 gallon water change weekly

 

[KJ]

Dinoflagates.

 

[lapin]

If in fact you have id them as dinos, The most common reason they show up is nutrients too low. Not sure what test kits you are using for everything but if they are accurate, then its my first guess as to the cure.
Also let me add (my opinion) Red Sea Pro is very high in alk. If you dont have corals consuming it you will run into a problem of it getting too high. This coupled with low nutrients and too much light can burn corals.

 

[mtdaly85]

As others have said: Dinoflagellates. One of the worst algaes you will ever cross. My advice is to read the stickied thread, identify your strand (you’ll need a microscope: you can get one pretty cheap on Amazon), and attack.

Bumping up the phosphates and nitrates, dosing Vibrant, and attacking with a 55w UV sterilizer took care of my Dino problem. Good luck man!