I use a Chemilizer proportioner with 1:100 ratio. It's a workhorse. Had bad luck with the Minidos proportioners. They just kept failing.
I use RO water and a 30 gallon holding tank. A small pressure sensing pump/bladder tank gives me good flow to water my 10 x 20 greenhouse.
I wish you luck! Even in my tiny environment, air movement makes a huge difference. Slippers hate you? That's too bad. Slippers love me, others not as much... Just want to ask you, how do you grow your vandas? Potted, wood/plastic basket, media/no media, watering, fertilizing, temps ect. You can pm if you'd rather not get this thread off track. Thanks.