Hi all, new to SW aquariums. Have had a FW one on and off for the last 5 or so years. Nothing interesting really, just a few basic fish, mechanical HOB filter and a heater in a 40gal (150L) tank.
I became interested in it as I love animals and am a SCUBA diver

and started reading about it on an Australian dive forum, which lead me to many forums and websites to research everything.
So at the moment... my setut (to be) is looking like this:
48" x 14" x 14", 40g glass tank with stand (already have)
Single 48" Gro-Lux 36W T8 fluro (already have)
External
canister filter (Eheim 2217, AquaOne CF-1000, other...?)
300W Heater
Crushed coral or aragonite
Live Rock (lbs...???)
I think that's all hopefully didnt miss anything.
As for stock just want to start out with a few hardy'ish fish, such as 2 clowns. Don't know what else yet... Now for the questions.
1. How much LR will i need?
2. How much substrate will i need?
3. What other fish are compatible and suited to that environment?
4. Is a skimmer neccasary to start with or can i add it later as need be?
5. A
marine aquarium I visited (only one i've visited so far) said I can just use the water from the ocean? Is this alright? [The beaches on the gold coast are very clean.]
6. Also what sort of filter should i get?
That is all I can think for now, any help is greatly appreciated.