What Kind of test is it ?
If its a piss test .. start eating lots of fruit and flood yourself with LOTS of water ( dont drink yourself to death )
If its a mouth swab test Just dont smoke for 72 hrs before the test and you'll be clean ..
I use my eyes to read ..
Home depot dont carry great nutes
Go here
a lot cheaper then most places
http://www.amazon.com/s/ref=nb_ss_0_10?url=search-alias%3Daps&field-keywords=fox+farm+nutrients&sprefix=fox+farm++