ammonia and nitrates

ok so i was at the fish store the other day (which, sadly, is only a petsmart, and their knowledge is very limited!) and the guy was telling me that nitrates turned into ammonia, and that my nitrates in my water were high, therefore killing my new fish and will soon turn into ammonia and kill the rest of them.
now, isn't it the ammonia that turns into nitrates, not the other way around?
i asked him and he assured me i was wrong. now i'm confused, and i'd just like to know which turns into which! just for future reference, in case this happens again!

either way, my tank is doing much better. i did water changes and bought a few more live plants, also returned my remaining new fish (for now!) to the store. no casualties for a few days, plus i have a few guppy fry!

ammonia comes out of the fishes' rear end and stuff that is rotting in the tank. bacteria turns ammonia into nitrites. another bacteria turns nitrites into nitrates. the only way to get rid of nitrates is to do routine water changes (or plants will suck them all up if you're tank is uber planted with a very low bioload.) i'd tell a manager that this guy is probably killing customers' fish lol.

here's a great link to a cycling guide that talks all about ammonia, nitrite, nitrates, and the whole process.
cycling guide!

so if you have high levels of only nitrates, try 2 50% water changes and retest

oookay that is what i thought, but since i had gotten my info from the web, i thought maybe i had it wrong. i need to go in there and teach them a thing or two, i guess...

not going to do much i'm sure.

thanks for the info!