Some question for Tonina tank

Hi, I'm a new member. And for the first question i want to ask something about Tonina tank. I've read some topic about the requirement for growing the Tonina. If I have to use the soft (low kh) & acidic (pH 5.5 - 6.5) water then when i turn on/off the CO2 the pH will fluctuate (I've tried in my tank kh around 2.5 while inject the CO2 and turn the light on, pH = 6.3 and without CO2 & light, pH = 7.3). The question is for the fluctuate pH like this is it effect with my Tonina? If yes how should i fix it?

Thanks,