Need some advice on red/purple slime

[eddfish]

Hello,
I need some advice how to get rid of red/purple slime with ton's of air buble on by sand bed and I always get lot of foam/buble on the overflow box and tank corners. I am using RO/DI water on the tap off. I only have few small fish in the tank with lots of softies/lps and few sps frag. I have two 250MH and two 96w Actinic running for about 9h/d. oh... I am using instant ocean salt. Any advice will be appreciated.

tank= 75 gallon
ph=8.3
temp= 80
sg=1.024
nitrite=0
nitrate=10
phosphate=?

 

[Chongpark27]

Check your phosphates and your filters in your RO unit, you might need to change them.

 

[Chiefmcfuz]

Test your phosphates, alk, calcium and mg levels see if they are out of whack, they can cause cyanobacteria. Once you find out which is your problem there are several ways to remedy it. Water changes, Phosphate removers, phosphate reactors, carbon, lowering lighting cycles, increasing flow.