My question is this; when the water level drops should I top off with plain RO water or the RO water nutrient solution based on manufacturers dosing levels. My setup is 5-gallon bubble buckets with aeration; 1000W CMH fixture and a very well aerated room using Advanced Nutrients products. Also, each week I drain reservoirs per manufacturers recommendations and refill with that week’s dosing schedule. I have asked this question of a few local growers and answers range from top off with full nutrients, top off with plain RO water and take a PPM reading and top off when PPM drop lower. The last seems like the best advice but better to ask first.
I top up with clean water once or twice a week and then clean out the reservoir and fill up with fresh nutrients once every week to 12 days.
Only difficult trial and error experiments can answer this, but logic probably gives the right answer. If your reservoir has the ppm you want, while its level reduces, then you must choose whether you want to reduce ppm from its optimal amount by adding plain water, or whether you want to keep ppm at its optimal amount by adding nutrients. On the other hand, if over-feeding has happened, as most people do when following manufacturers' recommendations, then adding plain water might be preferable, because the plants will avoid growth-stunting over-feeding. Don't over-feed, and top off with nutes to keep ppm optimal is what I do.
Advanced makes very hot nutrients; I never run higher than 1/2 dosing schedule. So I think I may play with the PPM approach especially as this is a last few weeks of flower.
My plants use 3 to 6 gallons of water per day . My plants roots take up 3 to 5 gallons of space inside the tubs they are growing in .. The math doesnt add up to use 5 gallon bucket I am using 20 to 30 gallon totes to grow in Sometimes I have to leave town for 3 or 4 days and the 20 to 30 gallon totes just barely hold enough water to last that long unattended. I also grow larger plants, 4 to 5 ft tall.