BRS RODI question

[poweraid]

If my DI resin is depleted will my TDS meter tell me? I,m having a problem with a rusty brown film on my sand bed (diatoms i think). I do 15% water change once a week and i vacuum the entire 2-3 inch deep sand bed as well. This stuff grows fast. within minutes of cleaning the sand it starts to grow. As far as i can tell my water tests within parameters (I only have crappy API color test kits at the moment)
Fish look good and corals are healthy and growing. tank has been up going on 7 months.and i only use water from my 5 stage RODI filter. TDS output reads 0 while input reads around 4-7. This is my first tank that i have had my own RODI. any advise would be helpful.:headwalls:

 

[Mrramsey]

Diatoms feed on silica... What kind of sand did you use? If it is diatoms they will go away when the silicates are depleted.

The di resin from BRS will turn from blue to brown and TDs on the output side of the do chamber will rise above zero.

 

[poweraid]

Regular crushed coral sand with a couple bags of live sand. If not diatoms then what else. It stands op to flow pretty well short of blowing my sand all over the tank. This has just recently started ocuring.

 

[Mrramsey]

Is it fuzzy at all cyano maybe.

 

[poweraid]

If I leave it alone it takes on a wavey jello appearance. Not fuzzy. Might have to go bare bottom.

 

[shifty51008]

Sounds like canyo to me. Up the flow and lower your phosphates and nitrates