[Patrick Guhmann]

I think important are constant water conditions. When you do water changes with water that has the same quality (RO water plus peat for example, same pH and conductivity) you can do big water changes. Once I changed 90% water without problems. But I think big water changes are often a waste of water, because you can clean the water with plants. Good plants for blackwater are Salvinia and Mayaca. I change water when the conductivity increases, so I keep this parameter stabil around a fixed point. But it depends on the aquarium. In my big 200l clearwater aquarium with Apistpgramma, I do not change water, because cond. is stabil at 15uS like my fresh RO water.