The only real iffy thing about using stuff you've collected from shore are chemical residues. Bacteria can also play a negative role, but that can be dealt with by soaking rock and shells in a bleach water solution. One parts bleach to 4 parts water. Soak for at least 30 minutes. Rinse well then soak again in heavily dechlorinated water. Rinse well and it's ready to go in the tank
Even if the items have been out of the ocean for a long time, you still want to soak in bleach water. You'd be amazed at the dormancy abilities of bacteria and viruses, so it's good to sterilize regardless of how long things have been out of the ocean.
Also I need 60lbs of live rock for my 30gal tank.. can I just get 10-20lbs of live rock and 40lbs of dead rock and wait until it comes alive?
YES YOU CAN!!
The bio and natural growth on the pieces of LR
will spread on over to other rocks. I like using lace rock. Great interesting shapes with holes; sometimes little tunnels. Great rock and generally costs the same as lava rock.
When the system is ready for livestock, try to wait on fish for at least a month. Focus on a cleaning crew like reef hermits, small snails, shrimps...especially a skunk cleaner shrimp. I never have fish in a reef without them. If the fish begin to break out with ich or is discovered to have some other external parasite, the shrimp will eat the parasites off the fish. Feather dusters are great for filtering small food particles floating in the currents. After the invert cleaning crew is settled, get a rock blenny. They're valuable algae eaters.
It's good to wait 2 weeks in between fish introductions...which this would make good time for a new fish in a QT. Two weeks is the average recommended time for quarantine. So, once the blenny has been in there for at least two weeks and the bio is stable, then you can introduce another fish that's been hanging in the QT for two weeks. Wait two weeks...then another fish, etc. These two weeks is typically the acclimation period for both the fish and the bio. It allows the fish to establish itself a territory and gives the bio time to populate to the new waste load.
Another good thing to keep in mind is to introduce lesser aggressives first. Damsels and clowns can be considered some of the more aggressive reef fish that aren't predators of the reef. They're fairly territorial, so try to get in any little gobies you would like prior to damsels and clowns. This order of introduction will help reduce tank aggression toward the new fish upon introduction.
We, as a people, know so much more about outer space than we do about our own oceans. This lack of knowledge can very well spell the dangers that lay in wait for us.
The oceans surely would swallow us before a rock comes down to smite the planet of it's life.