Just to chime in on how to save money with hydroponic nutrients, you could easily make a spreadsheet with the amount of nutrients in each bottle of the General Hydroponics trio (or any other brand and line-up), and take their recommended feeding schedule to calculate how many parts per million (ppm, or mg/L) they recommend each week. With this in hand, you could purchase the base salts (calcium nitrate, potassium nitrate, monopotassium phosphate, magnesium sulfate and a prepared mix of micronutrients are the ones I'm using) for extremely cheap and have hydroponic nutrients for years. I made very concentrated solutions of each base salt, and my spreadsheet calculates how many milliliters I need to add (I use a small syringe for precision) to some volume of water to copy whatever feeding schedule I'm using (in my case, I've made my own and I'm trying to work out what is the best feeding strategy).
It's a bit of work, but once everything is set up it's very easy to prepare solutions, with the added benefit of it not containing any dyes (which stain roots in hydroponic set-ups and can make it difficult to diagnose root problems) and being completely customizable. I've also added potassium silicate to my mix to add some silicon and also serve as a pH up. I still need to buy some phosphoric acid to use as a pH down.
Whenever I'm completely satisfied with my set-up, I'll tidy-up the spreadsheets and share them with the community.
