I use GH floa series nutes and the LUCAS formula...I never change the nutes in the res...always use the 8:16 ratio and/or rod water to bring ppm to 900 and ph to 5.8-5.6...that's it...I've not flushed or changed the res in 4 generations of my Snow White...She loves it and keeps getting better each harvest...

just use the GH Flora series and omit the grow part...add 8ml of grow 1st, and then 16 ml of bloom to each gallon of rod (distilled will probably work) water...water evaporates and you will need to add it daily and as you mionitor the ppm, you will notice the level in the res will go down as nutes are used...keep the ph at 5.6-5.8...