how to use a tds meter?!?!?!?!?

What does PPM mean? and how do i know what number im suppose to have?

ppm=parts per million
measures the amount of nutrient salts in your solution

how do i know if my ppm is at the right level?

the number is more of an idea to let you know how much nutrients you are feeding your plants...start low and slowly increase your ppms as your plants get larger.

if your plants look deficient bump up your ppms
if they look nute burned lower ppms

A good way to determine is to monitor your PPM between res changes. If the PPM is dropping with the water level it is ok to up your nutes. If the PPM is staying the same with the water level drop you are good or might need slight adjustment. If the PPM is increasing with the water level drop then lower your nutes.

haha got it thanks guys