Originally Posted by itxjohnlee
I think it will consider as hard water. You can use softeners
for this problem to be resolved.
First: Welcome to APC! This conversation was 10 years old, and not everyone involved is still active here.
Water softeners usually substitute sodium for calcium and magnesium, which isn't a good idea for aquariums. Even if you use potassium chloride instead of sodium chloride in the softener you are overdosing potassium and removing the calcium and magnesium the plants need. The best idea is to set up your aquarium with plants and fish that do well in hard water. Or, you can get a RO/DI filter system, and replenish the softened water with something like Seachem Equilibrium to get enough calcium and magnesium back in the water.