1. this is covered by the live rock, and a good skimmer, and often a refugium (many times a section of hte sump is the fuge)
2. 1-2 lbs per gallon...the closer to 2lbs, the better
3. minimum of 10 times per hour turnover, up to 20 times per hour. (using powerheads)
4. this is dictated by the types of corals you want, but 4 watts per gallon is a good 'minimum' amount for most soft corals (shrooms
5. no idea...my tank's not ready for corals.
some corals put off toxins to kill other types of corals...survival measure. using carbon in your sump/skimmer helps absorb toxins, reducing the bio-warfare in the tank.