I don't worry about VPD too much during night time, even in flower. The humidity is more important because you can easily develop mold/mildew/budrot during late stages of flower. 53% isn't terrible but somewhere in the 40s is more ideal.
Hey ReservoirDog! The metal screen is from an inline filter I put on the hose coming from the chiller. I don't use it anymore as I've gotten better at keeping a sterile res. Not growing at the moment but only a brief respite. I harvested over 8 lbs in the last year so I needed a break haha.
I use a 4" duct fan in my 3x3, it works more than enough. Still has negative pressure but it doesn't suck in the tent walls that dramatically. You can also open one of the ceiling holes, the light leak is not that bad.
It's personal preference. I like single plant scrogs, much easier. I've done 3x3 and 4x4. The 4x4 takes about 2-3 weeks longer in veg but you get a much larger harvest for not really much more work.
I use SNS 203 because I occasionally get thrips. Stuff works great but it is more of a preventative than pest killer. Spinosad is my go to if I already have the thrips.
In DWC you need less ppm than soil. Think of it like eating one big meal a day vs many small meals a day. I never exceed 1.0 ec (700ppm) at any point of my grows. The plant will be constantly snacking so you don't need as much. I normally stay around 500 during veg and max out around 650 during...