What is this?

[JustJoan]

Can anyone tell me what this is? I have had it in my saltwater tank for about 3 months. I have tried many things to get rid of it. It stays. Today I siphoned some into a glass, shook it up and ran it through a coffee filter. This is what happened after 30 minutes. What is it? Thanks to anyone who can help! It looks like a red/brown film on my sand.

 

[sixty_reefer]

Could you post some parameters and a full tank shot
Mainly po4 and no3

 

[JustJoan]

Could you post some parameters and a full tank shot
Mainly po4 and no3

I just tested. My nitrate is 20, my phosphate is .25 and my silicate is 1.5. I had a large snail die in the past 3 days and my pajama cardinal, although i never did find the body.

 

[JustJoan]

Could you post some parameters and a full tank shot
Mainly po4 and no3

 

[JustJoan]

My zoanthids are closed and have been for about 8 days. I tried peroxide dosing, did that for the last four days. No change.

 

[sixty_reefer]

How old is your system

 

[JustJoan]

How old is your system

2 years and 3 months. I moved to a larger tank last october.