Figured I'd better start a separate thread with my data. First, information about my test configuration:
250 gallon cubicle IBC tank (plastic bulk tank w/ metal cage, sometimes called a pallet tank) with rectangular opening cut into the top. A plastic flap is used as a loose cover to reduce evaporation.
Plumbing connections run through the opening on top of the tank.
Coates 1.5 ILS electric heater (1.5KW)
Little Giant 3-MD-SC pump (11 gpm)
Filtered by an Intex type A filter. The plumbing to the pump intake connects to a 1.5" bushing jammed into one end of the filter, the other end is plugged with 1.5" threaded plug (don't knock it, it works very well for a simple test rig).
Sartorius precision balance (for weighing the CYA Reducer product)
Hach DR820 Colorimeter with DPD Test 'N Tube reagents
Oakton pH2 EcoTestr
Taylor K-2006 kit
The test is being run indoors with artificial lighting. It has been rainy here anyway.
Water temperature is maintained at 80 degrees F.
TA = 110, CH = 175 (approximate values, not closely monitored)
I wanted the starting CYA to be less than 100 so no dilution would be required.
All CYA measurements are taken in the same position directly below a fluorescent bench light.
Product bag says one 226 gram (8 oz) bag per 25k gallons, so divided by 100 for my tank size = 2.26 grams. I don't have a skimmer & forgot to premix with water - I just dumped it in near the filter.
Data so far:
Date Time Total CL Free CL pH CYA
5/6 1:10 pm 3.20 2.86 7.5 95
5/7 12:57 pm 3.05 2.72 7.5 95
5/8 1:11 pm 3.01 2.59 7.6 95
5/11 1:19 pm 2.63 2.16 7.9 95 Added 14 grams of GLB pH Down after testing
5/12 12:49 pm 2.65 2.16 7.6 95
5/13 2:53 pm 2.31 2.03 7.7 90
5/14 1:49 pm 2.31 1.93 7.8 80
I will still be running the test into next week, so we'll see if something is really happening. If it is, my guess is that it just took a while for the microbes to grow & have a visible effect. But I dislike the disappearing dot test because I wonder if I'm imagining that I see the dot, or if I went slightly too far. Will have to see a bigger change to reassure me that it isn't just user error.