300 gallon reef

[someguy]

It sounds like you are fairly new into this process. A lot of the advice given here is good, but I would spend much more time doing research before getting any more equipment.
For basic chemistry, biology and equipment nothing beats the book "The Reef Aquarium" by Sprung and Delbeek. Most LFS will carry it, or it's pretty cheap on Amazon.
As far as online sources, this place is good, but for a tank your size, I would spend a lot of time reading the Large Tank forum on another site (I don't know if I'm allowed to mention it, but think of the words REEF, CENTRAL and .COM). There are many build thread of large tanks and much usefull information that is particular to large builds.