Acidity/alcalinity

My tap water is quite acid (between 7, and 6.5). It is also very soft (GH 50 ppm, KH 20 ppm). I was trying to correct this and I added some salt I bought in the pet shop: "SERA mineral salt". 5g of salt per100 liters are suposed to increase 0.6ºdH. I suppose 0.6º correspond to roughly 10ppm, but about dH I'm kindda lost.
I was wondering if this is the best way to adjust it and how to use it. Or maybe I should use some sodium bicarbonate, or some other kind of avaliable salt (food salt I find around here is with added iod and sometimes fluor or then mineral salt, so that could be a problem).
I was also wondering how I should take care of the acidity problem: are these products I find in pet stores the best/only solution?

Or are such values not worth the trouble and they are well accepted by the axies?

I'm having some problem having the N cycle ander control, so I don't wan't to have problem with this too...

Adding a calcium carbonate source will buffer the water against drops on pH (that is, increase the alkalinity), and will somewhat bring up the pH. The most recommended around here is to use some bird grit or crushed seashells to your filter, or in a mesh bag in the tank.

pH 6.5-7 is not acidic. It is very close to neutral, so I would not recommend trying to change it. As Kaysie suggested, adding a small amount of limestone or shells (any kind of calcium carbonate) to the tank is a good way to gently buffer the pH.