I have a new 20g setup with brown water and some brown algae. Most of these forums say it is because of silica. I wanted to be sure, so I had my water test. It turns out they were right:
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Date (mm-dd-yyyy) - Source - Test ID:
04-15-2015 - Office - 1 of 1*
Office - 1 of 1*
04-15-2015 Ammonia (NH3-4) Good 0 0.000 - 0.050 mg/L
04-15-2015 Nitrite (NO2) Good 0.005 0.000 - 0.100 mg/L
04-15-2015 Phosphate (PO4) Good 0.02 0.000 - 0.250 mg/L
04-15-2015 Nitrate (NO3) Good 1 0.000 - 25.000 mg/L
04-15-2015 Silica (Sio2-3) High 1.4 0.000 - 0.500 mg/L
04-15-2015 Potassium (K) Low 202 350.000 - 450.000 mg/L
04-15-2015 Ionic Calcium (Ca) Good 150 100.000 - 300.000 mg/L
04-15-2015 Boron (B) NA NA 3.000 - 6.000 mg/L
04-15-2015 Molybdenum (Mo) High 0.8 0.000 - 0.300 mg/L
04-15-2015 Strontium (Sr) Good 7.89 5.000 - 12.000 mg/L
04-15-2015 Magnesium (Mg) Good 1200 1100.000 - 1400.000 mg/L
04-15-2015 Iodine (I) High 0.18 0.030 - 0.090 mg/L
04-15-2015 Copper (Cu) Good 0.09 0.000 - 0.100 mg/L
04-15-2015 Alkalinity (meq/L) Low 2.2 2.500 - 5.000 meq/L
04-15-2015 Total Calcium (Ca) Good 350 350.000 - 450.000 mg/L
04-15-2015 Iron (Fe) NA NA 0.000 - 0.010 mg/L
Having test results like is very helpful as you know what you are trying to fix instead of just guessing. I am using live sand with RO/DI or LFS water and dry rock. I think the silicates may be leaching from the rock.
I got a Rowa phosphate/silicate remover and installed it in my filter. As soon as I did that, my protein skimmer exploded. I hadn't emptied the cup in several days and it was about 1/3 full of smelly gunk. Within 10 minutes of adding the Rowa, it had foamed over, completely filling the cup and flooding the tank with bubbles. Watch your skimmer carefully after adding any sort of rowa/phosban/seachem removers to your tank.