To get a better theoretical handle on Coco and it's CEC and how that affects feeding it, check this out
https://www.icmag.com/forum/marijuana-growing/growing-in-coco-coir/308425-the-chemistry-behind-coco-coir-a-strange-journey-from-ferts-bottle-to-to-buds?t=307683. Never water with plain water, you always feed it. You'll need an accurate TDS pen and PH pen. Pick an easy, complete nutrient like Jack's or Maxibloom. Then you just start with low ppms like 200, then slowly increase it as the plant get's bigger. At first you water it like soil, always keep it moist, but allow for a wet/dry cycle-don't keep it soaked everyday, while the roots are still growing. I like to "pot up" twice, I start in a solo cup, then pot up to a 1 gal, then up to a 3 gallon. This makes watering easier because it's very easy to overwater a tiny plant in a big pot. Once the plant fills up a solo cup with roots, you could feed it multiple times per day to runoff if you wanted-but at that point it's time to "pot up." Once your plant mostly fills out it's container with roots, you water it to runoff. Watering to runoff carries extra salts out with the runoff which helps prevent PPMs from building up in the soil. By the end of veg, depending on how big your plants are you will be feeding 400-500ish (some feed more but it's really up to your plants.) Once your plants are in their final container, and their roots have filled out, you will need to feed at least twice per day (in a 3 gal, in a 5 gallon maybe once per day) AT A MINIMUM. Some people feed their plants 5 times per day with an automated setup. Twice per day is a minimum that is easy to handle if you are just hand watering a few plants. Water to 10-20% of the volume of water as runoff. Also, keep in mind, every time I've said water here, i mean FEED. I never go over 700 PPMs in Coco, just don't see the need.
