PPM and Iguana juice organics

I use Iguana juice grow/bloom products . I read somewhere about organics not usefull to PPM meters? Should I buy a PPM meter or would it not help? I may have not understood the comment correctly?

I am looking at this meter. Is it what I should buy? I noticed EC rating on most plant descriptions. How do I understandd PPM and EC rating conversions easily with this type ppm meter?
HANNA Primo TDS Meter, PPM Tester, Conductivity link http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=270336297150



I've also read good things about Bat Guano Mexican and Indonesean as well as worm castings. Would It be helpful to add these products or overkill to my current Iguana Juice products?

Newbe

Thanks

let's try the weekend crowd.........