I was always wary of dosing using EI & dry ferts but took the plunge a couple of months ago, there is plenty of great info on this site for it. Although I have found several different recipes along the way, I now use Tom Barr's (as provided by aqua essentials) and have had no problems. I have the mixes set up for the specific tank in old Tropica bottles with which day of the week it gets dosed & how much written in marker on the bottle. I also keep the old 2l bottles from my Aqua+ conditioner and make up a 2l dose of NPK at a time, as I empty a bottle for a tank I just refill from the 'store' bottle. On the back of the large bottle I write how many grams of dry powders go in to make up each 2l. This way if I ever forget a detail it's right there.