Well, you added two of the most delicate and ich prone fish that are out there, If I were you I would keep the tank free of fish for 6weeks to let the ich parasites die, (I think some recommend 3wks but I like to wait a little longer). Then you need to set up a QT tank, all fish should go through QT for three weeks before being placed in the tank. Start with some hardier fish like clownfish or blennies or gobies. Put one fish in then wait a couple weeks and add another. Also get that ammonia level to 0 before you add any fish. I honestly don't think that we can keep our aquariums 100% ich free but you can reduce the chance by QT and by keeping the stress level low in the tank. Research any fish you are going to add to determine it's compatabilty and difficulty level. Do not add angels or tangs (may not want tangs at all, a 55 is really not big enough for a powder blue or most any tangs) until you tank is at least 6months old, these fish need a stable mature tank to live in.