Unless you have a specific condition (extraordinarlily sensitive fish, or you're trying to breed), you're probably better off just leaving it as it is.
Thats excellent advice from Bol, Koda. Messing with this stuff can cause an awful mess in the tank environment, even for those experienced in water chemistry.
And if it helps your concern, I keep several tropical community tanks with a General Hardness of around 20 degrees (~350 ppm), with no apparent ill effects.