Theory on the "brown sludge" algae

• pH: 6.7
• Temp:
• KH: 5
• GH: 6
• NH4:
• NO2:
• NO3: 10 before dose
• PO4: 1.25 before dose
• Iron:
• Dosing: 6.25 ppm KNO3
• NO3:PO4 Cumulative Dosing Ratio: 16.25:1.25 = 13

Notes:

The tank is crystal clear after the second run of the diatom filter yesterday.

I checked the CO2 rate, it had crept up to 2.1-2.2 b/s (KH 5, pH 6.7: ~30 ppm CO2), and though the fish seemed okay, I reduced it a bit to 1.9 b/s to stay on the safe side.

I hadn't been able to see any of the cherry shrimp for the past week, since I first put them into the tank, and I assumed that they must have died with all the water changes, flocculate, etc, but to my surprise, I saw two of the shrimp hiding out in the H. micranthemoides bushes. They were very red and looking bigger than when I first put them in.

The new leaves of the Echinodorus Kleiner Bar are growing in a nice bright red.

Ever since the green water, the plant growth has slowed down a lot. I want to avoid dosing iron/micro nutrients for a couple of days, at least until the plant growth picks up again. I have definitely observed that if green water exists, dosing iron/micros encourages growth in green water. On the other hand, I hope that a lack of iron/micros isn't the cause of a slowdown in plant growth...

I noticed that some of the "brown sludge" algae made a sudden appearance today. You can see a description of this type of algae in my algae gallery. I hadn't seen this sludge for the past couple weeks. Tom Barr has the theory that green water is triggered by ammonia, e.g. ammonia that may be released when you stir up the gravel during pruning/uprooting. I had purposefully added less nitrates after the water change based on the unscientifically based hope that lower nitrate levels would encourage the plants to soak up any extra ammonia instead and avoid another green water bloom. Now, I'm thinking that maybe low nitrate levels encourage the growth of this sludge. I dosed the phosphates as normal (1-2 ppm levels). I checked my past logs, and noticed that during the previous appearance of brown sludge, the nitrate levels had been < 10 ppm, usually around 5 ppm. The sludge's disappearance also seemed to correspond to an increase in nitrate dosing. I'm going to increase the nitrate levels tonight to see if that causes the brown sludge to go away tomorrow.