My wifes tank had a bad outbreak of gha. We treated, cleaned, replaced life rock, and water changed. Have kept lights low, lowered feeding, and made sure no direct sunlight is hitting g it. It is back and building up in her crushed coral. Help, not sure what to do next.... nitrates are spot on, ph is good, ammonia is nill. All the corals in the tank are flourishing. How can we best treat the substrate before we have it on her corals again and get it gone?