Huge swing in KH
3 weeks ago, I tore down my 115 gallon saltwater reef tank, in order to pursue a planted freshwater tank. I had a successful reef tank for 5 years, but to be honest, it started to become a little boring to me so I thought I'd try my hand at freshwater.
I'm encountered a problem though...........
When I initially started testing my water, I noticed very high KH readings. Upwards of 140-200ppm KH.
But then I checked it several days later and I'm down to 20ppm
What gives? I wouldn't think that the KH would change in time, like ammonia, or chlorine, or nitrates/nitrites, things like that.
I'm running Co2 during the day too.
I tested my tap water and sure enough, the KH is very high, back up to the 140-200ppm range, but I check the aquarium water and its fine. The aquarium water has been in there for a couple of weeks.
I can't figure it out.
My general hardness is very high too, arond 180ppm if it matters.
Any thoughts? Can KH just "dissolve" in time????