new tank

[bigblue]

what do the brown mean on my rocks?

[AABatteries]

Brown algae? If its brown algae I think that it means that your tank is starting to get established. I may be wrong because I'm just starting to learn SW.

[Dr.Fragenstein]

The brown is diatoms, the simplest of the algae you will see. It is the first colonizer in the tank and is easily wiped off the glass. Most herbivorous snails prefer diatoms over any other algae. Don't worry it is natural and will continue for some time. There are many stages of algae you will go through before your tank is more "mature" at roughly a year of age. Diatoms typically will always be around at least alittle on the glass that you will have to wipe off from time to time but will never be as "aggressive" as it is in the first month or two. Reducing silicates is also a VERY effective way in curbing their growth as the diatoms use the Silicates to produce their "cell walls".
I have a link to a thread I started on our local reef club on the first algaes and ways to fight them if you are interested.
Or you can get ALGAE:A PROBLEM SOLVERS GUIDE by Julian Sprung

Good luck and don't worry we ALL go through it!!