I was curious when people were adding the nitrate solution how much they were adding per week.
The way I understand it is that with the Nitrate/Molybdenum additive, you should only use it to achieve a ratio of 100:1 in regards to N03 & P04. Based on your previous mention, you should not have to use the solution since your at that range or better. (20ppm:0.15ppm)
Are you using GFO? You should stop if you are since GFO binds molybdenum which the chaeto needs.
Another question is are you dosing the iron & manganese additive on a daily basis?
If your chaeto is brittle, try dosing a Boron additive.