sorry, been a few days...Yes you are right. Dump rez(anytime you change nutes, flush, change photoperiods) then add a 33% solution back in...PH down is only 8bucks at the hydro store.

And I agree with the redneck...ebay has rofilters under 100bucks, all the time...Well worth every penny.

so the order of things is:
buy 3-part and ph down...necessary tools right off the bat!
ph pen and ro filter. (If you use R-O then you need calmag+ to replenish the minerals you removed. this si a good thing, because calmag+, as well as 3-part) is buffered to help keep you ph close. You still need that pen.

Ebay has them for 30-50bucks. goodluck. lw

If you have these things then you can do a nice grow, then learn to add things. Some fol