Quote Originally Posted by dougefresh
one last question.? How often would you recommend changing the water and nutrients in a hydro system (because I change it every 3 days)? and is tap water acceptable or do you have to let the water sit out so the chlorine evaporates?
Depends on some things, but don't go longer than 1 month between changes. I try to do it at least every other week, but often don't quite make it. If you top off your system often, you will need to change your reservoir less often than if you don't top off very often.

Tap water is fine, just keep in mind a couple things:
- If you live in the city, you probably have too much chlorine in your water. (Plants actually need a small amount.) This must be remedied either by letting your water sit out several days, or by getting some chlorine neutralizing liquid, or by getting a reverse osmosis machine. If the latter is the case, be sure to add something like a product called CalMag, to put back essentials it takes out.
- If you use city water you will need a chlorine test kit, or you can ask your water company for an analysis of your water. You'll probably still want a kit so you can know if you are neutralizing the chlorine correctly.
- If you use city water or well water, your tap water will come complete with it's own set of nutrients, usually between 50 and 350 ppm. Be sure and count this when adding nutrients to your solution so you don't burn your plants with to many PPM. You should consider buying a PPM meter to eliminate guess work.