So sorry to hear about this. I am sure it feels bad, but with a little effort you can solve this. You need to do two main things. First you need to treat your pet fish. Capture and place all fish into a quarantine system. The ideal here is having two tanks/tubs to allow you to follow the tank transfer method. You can also treat the fish medically during each of the stages to improve their health. (For more info on quarantine checkout Humblefish's post on reef2reef or watch reefdudes latest livestream on youtube) Secondly you need to eradicate the ich from your display tank. As already suggested by the fellow reefers above you need to 'fallow' your tank (ie remove the fish). By removing the fish the parasite has no host, so will eventually die. The longer you leave the tank the better. At 3 weeks you will have a c.66% chance of eradicating the parasite, but if you leave it for 6 weeks this goes up to c.95% and c.98% at 9 weeks. The common practice recommend is 76 days. The good news is once you go through all this you will have all the skills and equipment to fight off any future issues with your fish. Good luck! Sent from Singapore Reef Club mobile app