Below is the procedure that we worked out (see earlier page of thread below) for increasing the GH using calcium chloride and magnesium sulfate. This procedure is faster and better than adding oyster grit to the filter. It shouldn't increase the pH.
This procedure is designed for very softwater aquariums where GH = 0- 6 and plants aren't doing well)
Steps in Procedure:
- Measure starting GH of your aquarium water
- Prepare concentrated solutions of each chemical (MgSO4 and CaCl2)
- Add a small portion of Mg solution to the aquarium and measure resulting GH increase
- Add Mg solution until you get about what you want (I'd recommend a GH increase of about 1-2, no more)
- Then start adding the Ca solution until you get a GH increase that is 4X that of the increased GH due to Mg
- The final GH should be over 6, preferably around 8
http://www.aquaticplantcentral.com/f...ht=Equilibrium
Calcium Dosing Procedure 
Threaded Mode
