I use a peat bag in a small auxiliary canister which powers my surface skimmer, and change it every 2-3 months. And cut my hard water 1:1 with R/O. When the water gets a little tinted I’m good. Although I have a degree in chemistry, this is really a gardener’s approach. Have added alder cones and almond leaves, but per the above suggestions, will toss in a few more cones to boost things in the new 75g Amazon tank.