Picked up a 100gal saltwater tank with living coral and a few inhabitants. I'm just starting fresh so any help would be greatly appreciated. Original owner had this tank for about 10 years, almost 95% self sustaining. I picked it up from the second owner after he had it for only about 3 months. I don't know anything about live coral, how they respond to stress, and what are the signs of unhealthy or dying coral. I saved about 90% of the original water so only a 10% change in water, salinity was high so I just added filtered water until it was just right. there's a 10 gal sump underneath with a protein skimmer, wasn't to sure about when to run that and for how long? Just take a look and if you can try to give a basic rundown on how to keep this tank in tip top shape I would be so grateful. Thanks