I would like to introduce you guys on sphagnum moss to replace ketapang leaves. S.moss acts the same as ketapang, will give you black water and reduce PH. But it has a special property thats advantage to other softener, s.moss is able to reduce TDS in your tank water. Simply put them in a fine netted bag, tie it and dump the whole thing in the water. You may add some pebbles to sink it. replace every 2 months. Buy them at any plant nursery, will cost you around RM10 for the whole bag. Economical yet useful. This is how I do it, i dont even bother with the pebbles the darn thing will sink in a weeks time. This is my sump tank btw.
Fishiology - is a nonscientific study of fish, a branch of Aquarist