@Colin, this is carrying on from another thread, here:
I use Flourish COmprehensive Supplement 2x a week (dosing 1 ml each time, my tank is 52l), FWIW in my 3 x 50-60l tanks I use 0.5ml once a week and that is adequate. I have quite a lot of plants. My water is also very soft.
www.fishforums.net
There are some unknowns in this. First, the water is forest stream water. The GH and KH are 2 ppm (if memory serves me, but they are very low) and the pH is fluctuating in the stream water. This may be related to the environment, which can fluctuate seasonally.
Then there is the Flourite substrate. Seachem claim it does not alter pH; I had it several years back and frankly I cannot remember one way or the other. I only know it was next to useless as a substrate and after two years I tossed it in a hole in the back yard and buried it.
@Banafish is there any other substance in the tank? Like the Flourite, wood, rock...or added water substances/additives...anything at all.?