Is it possible to raise pH in RO water without Na, Mg, K, Ca, S addition?

Maybe the question in the title is simple (=stupid) and the answer is 'simple No' but I have the urge to ask. 


Some background, I have an aquarium which I use RO water and I use some portions of $\ce{KHCO3, MgSO4, CaSO4}$ to raise my GH and KH and in result, I get also an amount of $\ce{K, Mg, S, Ca}$ + (bi)carbonates in the water in a specific $\pu{ppm}$ quantity and ratio between them which I want to keep it stable.


Still, after the additions of the compounds above, I get something like 1 KH, 3 GH and pH of 6.4 but I need to raise it around 7. 


Is there any other way to do it without another compound? (preferable no baking soda or soda ash) 


Thanks!


