Uv sterilizers help by killing algea spores and ich parasites.
If you decide to get one i recommend a gamma uv. Great quality.
Most important thing to help prevent ich is carefully look at the fish you plan to purchase.
Look for scratching,wounds,abnormal breathing,and salt looking parasites.
A qt would help too.
Also keep the tank stress free as possible.
Smaller water changes(10 % every 2 weeks),no fighting, and good water quality.
Some fish are more prone to ich than others.
Such as tangs and angels.