I have found myself in the posession of a small DI unit.

I know a bit about DI water and I'm really excited to use it to process
my 'liquid rock' tap water.

I know that they sell additives to replace trace minerals and salts to
DI water. Can I simply mix DI water and tap to get the right GH? I'm
worried that the wrong PH buffers in any of these additives may increase
algae blooms.

I know you can't measure the pH of DI water. My goal is to try to get
soft and slightly acidic water (peat treating if neccessary). If I mix
DI and tap, can I check the PH?

Thanks!