I do seachem liquid ferts, no gh booster. It drops for about an hour, then sits at 730-750 until I change it, or I see it start to rise. 750 seems to be about perfect for my tank. My convicts just paired and about an hour ago I watched him hump the slate wall.
I turn my fluval 305 off 30 min before I do a water change. I made my own vac out of tubing from ace. Sucks the buttom but doesn't kick up poop everywhere. I change the water, turn it on full blast and gradually kick it down to the 3rd notch when i see the tds reach where I want it. I let the water sort its self out. It took some trial and error.
R/o is just blank slate water. If you have good bio in your filter it will blend quickly.