Tank recovering after years of increasing water hardness
I've been running a twenty gallon Eclipse 2 for eight years not dosing anything and topping off with tap water. There were two Angel Fish with some anubias, Java Moss and Java Fern. The fish died after six years a month after some house sitters introduced some surprise fish to the tank when we were on vacation. I'm not saying that was the cause of their death, but maybe. Then I put in two fish that I had been keeping in the garage a few years. They are still here and seem to be happy. One of the fluorescent fixtures failed about three years ago and I lost my Java fern and damaged my anubias. The Java Moss hung in there though.
The tap water is about 130 ppm KH. But my aquarium water got to 270 ppm KH because I wasn't topping off the tank with RO water. I am gradually decreasing the water hardness with RO water. The light has been replaced with an LED light strip and I'm dosing fertilizer and injecting CO2. When the fish are gone I will replace the substrate with Eco Complete. In the meantime, I'm using plant tabs that I'm really not happy with for some new Wisteria. The Wisteria is slowly responding though.
As has been posted before in these forums, even if your tap water is about right, you should top off your tank with RO water to keep your water hardness from building up too high. I should have realized by the calcium deposits on the outside of the tank left by splashed tank water.