Diatoms?

[oddmegameg]

Hey there, our 37 gal that's been up for about 3 months was doing great until about 2 months in. Our levels have stayed consistenly in the correct ranges, although I've noticed that our phos and nitrates are 0. I attempted to place Phosguard in our filter to possibly remove some of the phosphate and possible silicate. Which after removing the brown from the glass and surrounding rock, seemed to keep it from coming back immediately. There are currently 4 corals in the tank, all which have seemed to have lost their color, and or how much they extend. We do 10% water changes once a week but the brown stuff seems to return within the next day. Within the last week, we have noticed lengthy brown strings on the live rock and coral frags. There are no aquatic life in the tank other than the corals, no fish, or snails. Would adding fish help the balance of nutrients? Should I dose with nitrate?

 

[blaxsun]

Wherever possible you want to avoid nitrates and phosphates bottoming out. I would look at adding some cleanup crew - as not having any is probably contributing to some of your issues. You may also need to supplement their feeding with a quarter sheet of seaweed 2-3 times a week.

I would look at a few trochus snails, a similar amount of spiny astrea snails and twice that number of ring cowries (they specifically need to be ring cowries). I'd also add 1-2 small blue hermit crabs.