DI water, pH, TDS, fertilizer, KOH, ProTekt, TRIS?

[tropterrarium]

Just measured the pH from my DI water and it is <4, a tad acidic. There are several options of adjusting it:
- add tap water, about 25% of DI volume, gives pH of ~6 (I use a simple drip/color match test) and TDS of 50 ppm.
- I could add KOH, work in a lab, so easy to get some. Given that DI water has very low buffering capacity, I wonder whether it will go from 6 to 10 with a single drop of 1N KOH. Haven't tried that yet. Any experiences? Will skew the npK ratio a bit, but don't think that matters.
- There is also the infamous TRIS buffer. Have not seen anything about it re plant water, so wonder whether anybody has tried that.
- Dynagrow has a pH-up adjuster (Protect), most likely a buffer like TRIS, just at a higher price. So, worth it? I use Dynagrow liquid fertilizer, so that should be compatible.

What do you do? Any experience, good bad ugly?