Weird growth on sand bed reddish brownish ideas advice?

[nightmarepl]

Been having this for a good year now i do 2-3 week water changes roughly 10 gallons per change tank is 75g sump is around 30 gallons
Ph 8.0
Nitrates 10ish
Phosphates are 0.86. On hanna
Temp 77
Hard to take a picture of it but develops on my sand bed first starts off reddish then gets brown / greenish
Eventually get it on my rocks and it’s reddish
If i hit it with chempure it kills it in 2 days but returns in 2-3 weeks any ideas?

 

[KING KONG]

Been having this for a good year now i do 2-3 week water changes roughly 10 gallons per change tank is 75g sump is around 30 gallons
Ph 8.0
Nitrates 10ish
Phosphates are 0.86. On hanna
Temp 77
Hard to take a picture of it but develops on my sand bed first starts off reddish then gets brown / greenish
Eventually get it on my rocks and it’s reddish
If i hit it with chempure it kills it in 2 days but returns in 2-3 weeks any ideas?

My guss is cyano(pics r not clear and I am on phone). Cyanobacteria loves still water and light. Whatever it is u can remove it by directing a powerhead to it and removing it daily. Reduce white light. U can also try hydrogen peroxide(1.5 ml per gallon). Certain types of snails and starfish also eats it. For me powerhead had done the job when I got it few yrs ago as they prefer low flow areas to grow. granulated ferric oxide to remove excess phosphates in the system. Check to make sure you are not feeding any foods that are particularly phosphate rich. Almost all foods when converted by animals will add to the tank's phosphates levels, but prepared foods like seasoned nori, liquified foods, gels and low quality fish meals tend to be higher in phosphates than other foods. Cyano tends to grow faster in warmer water than in cooler water

 

[TheBear78]

I had similar problems when my phosphate jumped up. It kept climbing from 0.08 to around 0.6 with nitrate always around 30. I've gradually bought them down with Rowaphos in a reactor and now I'm maintaining around 0.3 and 35. Everything thing else appears happy and the algae which I always assumed to be Cyano is receding.