Triggerfish suffering from marine whitespot
Ick goes through four stages: theront, protomont, tomont and trophont. The most obvious stage when most hobbyists become aware of the disease is the
Trophont stage. This stage is the feeding stage of the life cycle. They feed on the body fluids and tissues of the fish. In really bad cases it's possible for the fish to die.
They mature anywhere from 3 to 7 days depending on the temperature of the tank (higher temp speeds up the process) then they detach from the host, fall to the bottom of the tank and develop in to protomonts.
Protomonts will move along the surface of your rock and substrate to find a safe place to hide and begin to form an encrusting surface while they evolve into
Tomonts. This usually lasts 2 to 8 hours with the encrusting layer taking up to 18 hours to fully harden. Tomonts are the reproductive stage of the disease. Once the tomont is completely encrusted, it can't be treated with meds. The tomont begins to divide and can reproduce up to 1000 new protozoa called tomites. It takes anywhere from 3 to 70 days for the tomites to fully develop and hatch into theronts.
Theronts are free swimming protozoa looking for a host and only have up to 24 hours to find one before they die off. Once they find a host they become trophonts. Knowing the life cycle will help understand how a lot of people think they have gotten rid of the ick and complain at a later date when it keeps coming back. Often people only treat the tank for the trophont stage and ignore the rest of the life cycle since it's not appearing to infect the tank. In order to completely get rid of ick, you need to ensure that you continue to treat your tank until all the life cycles are completed and everything is killed off or your fish will keep getting re-infected.
Although copper is the best method of killing ick, it's extremely harmful in a Marine tank and will kill your beneficial bacteria, inverts, live rock, live sand and it is extremely difficult to remove from a tank after treatment. Other ways to get rid of ick, is to remove all fish from the tank a few degrees (around 82 to 84F), increase the temperature of the tank to speed up the life cycle of the marine ick and let it die off in the theront stage of life. Meanwhile, treat the fish in hospital tank with an effective medication. (Check your LFS for recommended meds and see if they have copper in it) Don't stop the treatment once the visible symptoms are gone, chances are it'll still be alive even in the hospital tank. If you can get a reef safe treatment then it'll be possible to treat your fish in the tank, but I don't know how effective the treatment will be, again keep treating the tank for 4 to 6 weeks to ensure that you kill all the protozoa
Marine ick is a protozoa called Cryptocaryon irritans. Couple other common names for the disease are white spot or crypt.
The common name, ick (ich), comes from the freshwater counterpart, Ichthyophthirius multifiliis. But the two conditions are unrelated. It's introduced to a tank from fish, live rock or live sand that have been infected with ick at any different stage in it's life cycle.