I've read that to saturate the soil to where it is just starting to run off, is that correct?
-Yes thats a good indicator that your plant has enough water.
Would that be a proper amount to feed the plant?
- No, that is an indication of how much water your plant will consume, the feeding your asking about would be the PPM concentration of your nutrients. Depending on what type you are using there are different
strengths for each stage of development. For example I use General Hydroponics and they have feed charts on their website to go by. A tds meter is very helpful and can be had for under 20$.
Do I get rid of the rest of the gallon of water/nutrient mix or save it for next feeding?
- I dump the rest of mine out when I am done, I suppose with an airstone it could be kept going similiar to a dwc.