As we learn together...
Using a liquid PH test kit is perfect for fluctuation. You make the water PH 6 to your eye but it'll be a tad higher or lower too. You can't see the difference in 6.0 and 5.9/6.1. When you make it 6 it's going to be one of thoes three. Now, you can faintly see 5.8/6.2 and that's ok too.
All I can say about PH is keep it simple for success every time. When you get everything balanced (rockwool, media, water) and keep making 6 water you really won't have to worry about ph-up/ph-down and have your fluxuation.
Having a liquid test kit as part of your equipment is a must, weather you prefer meters or not. Ever have a meter go wonky, rez full of new water you thought was 5.8, waiting a week for a new meter that didn't come with calibration packets, wait another week as your plants turn to crap. I did and it sucks. Bad.
Always go with manufacturer recomendations! Oh, and spending 150$ on a quality meter is a huge waste of money, stored properly or not, it will fail in less than three years. For a one time purchase I could have enough solution to last the rest of my life. lol. Never fail.
Hydroguard and DWC are married. Without one there is no need to grow
Aerateing water while declorinating is a personal preference. When I found out there is no need to aerate I stopped wasting my time.
Light being ok in your rez is nonsense. What? Why would you say it's ok? Even the light that seeps in through a clear airline is bad. Light just creates another issue with your water, causing more problems, more money spent to cure them and loss of bud.
Also, why would you talk about things I didn't bring up if your not going to bring them up yourself? It's ok for you to cover them as they come up but I'm expected to clever them beforehand? You got me giggling dude.