Re: nitrites STILL won't go away
Posted: Wed May 25, 2011 3:33 pm
This was the information in which I was referring:
RTR wrote:Quite a number of the chemicals involved in our hobby test kits are the same for FW and SW, but, big BUT, the color scales are not the same. In BW and SW, the increasing mineral content of the water distorts the colors of our colorimetric tests. SW test kit charts correct for this discrepancy, but linearity is not perfect. That means that we have a hard time getting exact info at varied BW levels. The tests are pretty good and highly reliable or repeatable (if your techniques are OK) at FW & low BW, and again at very high BW and low SW to full SW. In between we have problems but we deal with them. The manufacturers do not give us a lot of support in mid-BW, but that is not callous, it is just too expensive for then to make a whole set of test ranges accurately. Very, very few folks would buy 3-5 full sets of tests to cover FW through BW to SW, so the manufacturers don't produce them.
The best suggestion I can offer is to use both SW and FW kits and guestimate the mid-range results, knowing that neither kit is going to do the job alone, but together will get through the range where it is uncertain. Because the nitrification switch-over is ~ 1.008 -1.012, that is the single most worrisome area. We generally suggest that folks go very slowly through that range. Outside of that, the accuracy of the other readings in less critical.
HTH