When using dosers or wanting to measure liquids instead of weighing powders each mix, a stock tank is necessary. This turns your dry powders into concentrated liquid form that maintains the perfect nutrient ratios.
To start making a stock solution you will need what we call stock tanks. You should have stock tanks that are all the same and marked with volume increments so you know how many gallons to specific fill lines. If you don't have fill lines you should estimate your fill line and make a mark at the same place on each tank so each tank gets the same volume.
After you have finished marking your tanks you can start filling one with water. You should fill the tank 70% with water and then add the powder, lets say Part A. You will very heavily mix with a paint mixing or mortar mixing bit for a few minutes. Then you can continue filling with water while still mixing. Stop filling once you hit your fill line. It is very important to HEAVILY mix and make sure its dissolved.
Next you will move on to the Part B tank and repeat.
One thing we recommend is adding a cheap wavemaker to each stock tank. This is by no means required but it ensures that the mix is fully dissolved if it wasn.t mixed well enough. They attach to the tanks via magnets and can be slid down the tank from the outside and pointed towards the bottom of the tank to stir up anything undissolved.
One mistake we see often is mixing stock tank solutions incorrectly. The volume of the stock tank is water + powder = total volume. If you're making a 55 gallon batch you shouldn't be adding 55 gallons worth of powder into 55 gallons of water. The volume of the powder is included in the total volume. This is why we fill roughly 70% full, add the powders, then fill to the final mark.