I think a piece of cultured live rock mixed in with the rest of the rock works as well as anything. Don't think the bacteria cultures work well at all. I also don't think there is such a thing as a tank with no ich circulating in the water. The key is for the fish to be health enough that their slime coat protects them. Like a dysfunctional immune system in a human, there is always something in the environment that will attack a fish that isn't fit. I did use a UV
sterilizer in an effort to rid the tank of all the unhealthy organisms in the beginning and now that everything has been balanced and running for 20 years, I no longer use it. Not even sure it did me any good early on. Would like to hear the opinions from the rest of the crowd.