ok so as the name implies, I am fairly new at this and I have a 55 gal that was up and running for the entire year, some parasite has caused all of my fish to die,I thought it was ICH because I saw the fish scraping up against the gravel and objects in tank, so I treated with medicine for that, raised temp all to NO avail, all fish are gone and I find myself starting over,how long should I wait to start again, should I do an entire water change, 50% ? any advise would be greatly appreciated ...