Sufficient PO4/NO3 in water?

• pH:
• Temp:
• KH:
• GH: 8
• NH4:
• NO2:
• NO3:
• PO4: 0.35 before dose
• Iron:
• Dosing: 5 mL iron chelate (0.5 ppm), 15 mL KNO3 (3.75 ppm), 10 mL KH2PO4 (0.4 ppm)

Notes:
There seems to be slightly less algae/cloudy water today. The brown sludge algae? was gone in the morning, though it came back to a certain extent later in the day. It makes me wonder if the plants do better (and algae does worse) if there are high enough concentrations of NO3 and PO4 in the water. I dosed some phosphates/nitrates for tomorrow to see if that helps beat down the algae.

I've found a link on a forum with exactly the same description of the brown sludge as mine:

• It sits in little piles on top of the plant leaves, but otherwise does not seem to particularly attach to any plants or gravel. It does not have any threads or filaments.
• The brown sludge blows off easily. Stirring the water currents will easily blow it off the leaves of the plants.
  
• It has a goopy, slimy brown appearance that are shaped in brown droplets when suspended in the water. In this way, it seems to differ in appearance from brown diatom algae, which is usually a little coarser in appearance and more clumpy.
  
• It disappears by morning but grows back over the course of the day.
• It seems worse right after a water change.

I'm wondering if there is some relation to either the water hardness or perhaps even excess potassium. After the 50% water change, I add about 35 ppm of potassium via the Equilibrium. Now, if there is potassium left over in the other 50% water, the levels could be even higher. I also noticed that the posters tank parameters all had GH of 8 or higher. I don't know if there is any relation of a moderately high GH to this problem. I'll keep this in the back of my mind. I might add less Equilibrium at the next water change to soften the water up a bit. There's also been a lot of rain lately in my area, so there might be a change in my water supply (water runoff mixing in more minerals) that is encouraging this brown stuff to grow.