jglover
Aquarium Advice Freak
I looked up the chart on the link. You just match ammonia total, ph and temp to get free ammonia. Unless I've done it wrong there looks to be a huge difference between the table and the alert? I'm quite interested in this as table theory vs reality according to the alert.
There's not really a huge difference between the two. The ammonia alert is a semi-qualitative test, the API test is a semi-quantitative test while the chart is a calculation. All things considered, the chart should be the most accurate, provided your input data is good.
I would imagine the ammonia alert will have the largest margin for error, it's 95% confidence interval is likely huge. There are also a lot of compounds that interfere with these test. I know for the API test, calcium and magnesium can cause false positives if the levels are high enough. Not a problem in most freshwater tanks but could be an in issue in brackish or marine tanks.....hence the difference type of kits for marine water.
The difference seen here is only a factor of 3x, so it could be well within the confidence interval of the ammonia alert. I've never seen the QA data published for the ammonia alert.