Black water extract use mostly for look and making fish feel safer in that environment, you have to use chemical to buff your water OR if you want to do it nature by add ton of driftwoods, extreme heavy planted plants then your water will soften in few weeks, the problem is that most ppls do very large water change each time so pretty much all water parameters will be back almost to normal after that lol
*I knew most folks will disagree with me but I have 1 of my heavy planted tank with fishes that I never do water change for years (at least 4 years now) and only top off the water that lost cause evaporation each week (I add trace water element 1 time a week).
