I wondered about O2 saturation so thats good to know.

I don't think light is my problem - or rather the limiting factor in my setup. I have 220 watts of compact flourescent lighting over a 72 gallon tank (w pressurized CO2 monitored at 6.3 pH - KH measuring 4 after water change) which I dose accordingly:

Day 1: 50-60% water change followed by 1 teaspoon Barr's GH booster, 1 teaspoon KNO3, 1/4 teaspoon of KH2, 70 ml excel

Day 2: 20 ml flourish, 10 ml excel

Day 3: 1 teaspoon KNO3, 1/4 teaspoon of KH2

Day 4: 20 ml flourish, 10 ml excel

Day 5: 1 teaspoon KNO3, 1/4 teaspoon of KH2

Day 6: 20 ml flourish, 10 ml excel

Day 7: stare at tank and wonder why I don't see more pearling

Looking at the EI recommended dosage schedule, I expect that this dosing schedule provides a little more than my plants need. And with that much light..... I'm surprised my plants aren't pearling/growing more (fairly new bulbs btw). I considered O2 saturation, but I suppose thats no longer an answer.

I also considered that I was miscalculating CO2 so I installed a drop-checker, but that indicated good levels of CO2. Although, I must admit that I didn't pay too close attention to the posts on this step. I filled the bulb with water from my tank (4dKH) and added about 10 drops from the reagent that came with my order.

Other than this I contemplated poor water flow as a reason for less pearling. However, my experience in the past with better performing tanks was that if I turned off the filter the pearling rate increased - or at least appeared to.

I've read enough posts and been doing this long enough to know that I'm missing something right under my nose...

Ideas?