You should change the nutrient solution once a week even if your topping it off in between.This thread should help you with your nutrient questions.

http://boards.cannabis.com/hydroponi...rt-calmag.html

Here is a great online supplier for most hydro needs.

High Tech Garden Supply
socialistpete Reviewed by socialistpete on . first hydro go :) well im definitelygoing with the dwc method. got a few questions that i cant really find definitive answers to so i'll ask em here and make it a lil easier lol: 1. where can i get rapid rooters? 2. can i do a dwc in a large rubbermaid tub? 2b. how many plants should i do max in one large tub?(size to be determined once i purchase it after knowing if it will work in a different container) 3. how many lights will i need? and wattage? 4. how do you determine what you want/need for lighting Rating: 5