Water Conditioning.

Hi, Advice needed I am setting up some new (second hand) fish tanks the water has been in several days and is up to temperature, I checked the water this evening and the results are,
GH 5
KH 4
PH 6.5

Now I want the conditions to be, GH between 8 to 12 (say 10)
KH whatever
PH between 6.6 to 7.0
Any advice to obtain the above conditions would be appreciated, I should add I intend to use air driven box filters so and additive to them would be ideal.
Thanks,

have you tried adding bicardanate of soda that hardens the water and puts up the ph its a long time since i used to do it
or add coral frags to a corner bubble filter that adds calcium and puts up the ph in the same way

Hi Mick, thanks for your suggestions, I think I like the coral frags idea best, bicarb may be too unreliable but the coral should be there fir yonks, cheers