Sorry for the late reply. It could be the iron.So I tested the water just to see if nitrates creeped up. Ammonia 0 nitrite 0 nitrate 2.5ish.
So I'm thinking either my caribsea sand is still leaking silicates, the mexican pebbles are or my tap water has high phosphate.
I've been doing 2 66% wcs a week due to the medium to high bio load. I think it might be removing too many nitrates and not having enough for the plants. This could explain high phosphates in my water since I'm doing 2 large water changes.
I'm going to cut it down to 1 66% water change per week and see if the nitrates rise up to around 10 and if less new tap water will help with lower silicates.
I ordered an api phosphate test kit coming monday to check my tap water.
I dose flourish and flourish excel as well as iron and potassium.... do you think overdosing any of these could cause diatoms?