This is a great read for anyone that has marine ich problems. I copied it from www.reefsanctuary.com , originally written by Lee (leebca) who has given me permission to repost.

Marine Ich (Cryptocaryon irritans)

One of the marine aquarist’s devils. So many articles have been written about it. Many are long or are in multiple parts. A lot is known about this marine fish disease because of the many $$$ put into research by the fish farming and aquaculture industries. First discovered (or the better word is 'noticed') in the 1800's and later more understood in the 1900's, we’ve learned about all there is to know about this parasite by the 2000's.

I don’t want to write a long post on Marine Ich (MI) but the reader, in as brief of space as possible, should know some truths. The aquarist 'sees something' and then 'guesses' as to what it means and thus starts another round of rumors. It's almost a type of voodoo. It's easier to listen to a rumor of a short absolute statement then it is to read and understand the results of decades of studies and experiments. It is easier to try and take shortcuts with this disease by believing the parasite to be able or capable to do things or die from things it just can't, then it is to do the work to kill it, control it, or prevent it by the means that are known to work.

It's time to separate out the rumors from the facts and the subjective observations (which start rumors) from actual scientific studies. In bullet form, here’s what is known:


Life and Visuals:

1, The parasite has several ‘stages’ in its life cycle. Cyst in aquarium (usually on substrate, decoration, wall, equipment, or rock) ruptures into free-swimming parasites that burrow into fish, grow into a visible white nodule that is ‘pregnant’ with more parasites, that usually falls off the fish to form a cyst that starts the cycle over again.

2. Only time a human can see this parasite with the naked eye is when it is ‘pregnant’ on the fish and has formed a white nodule. (The white spot is about the size of a grain of table salt or sugar).

3. Parasites that have just burrowed into the fish are not visible until 2.

4. Cycle can be completed in less than 7 days, but usually within 24 days BUT can go as long as 72 days. Literature usually quotes ‘average’ number of days. 72 days is rare; 60 days usually encompasses more than 99.9% of the observations and research.

5. This is not the same as the freshwater disease, Ich (Ichthyophthirius multifilis) but it was named after it?! This leads freshwater aquarists to thinking the wrong things about Marine Ich, adding to the myths and rumors.

6. MI is not very sensitive to temperature changes. That is, increasing the temperature does not significantly decrease the life cycle time. This is not true with Freshwater Ich (which is where this rumor of raising the temperature on a marine aquarium with MI comes from).

7. MI can live and reproduce in temperatures as low as 50F and as high as 90F. Thus temperatures that would kill MI would first kill or severely stress most tropical marine fishes.

8. Spots appear then disappear as MI goes through its cycle. Remember 2. This 'disappearing act' is what leads uninformed aquarists to believe the fish are cured. This is the dumbest thing aquarists can possibly think about this parasite!

9. Parasite likes infecting the fish’s gills. The tissue there has more water passing by so there is an increase in chance the free-swimming parasite will get to the gill. This is one reason why fast breathing (over 80-90 swallows in one minute) is one of the symptoms of possible infection.

10. The parasite burrows into the fish, below the mucous layer and into the skin. (This is why cleaner fish/shrimp can’t get to it in order to remove them from the fish). The second dumbest thing an aquarist can think: I'll get some cleaner fish or cleaner shrimp to remove/eat the parasite. THESE MARINE LIFE DO NOT EAT THE PARASITE NOR WILL FISH OR SHRIMP REMOVE THE PARASITE FROM THE INFECTED FISHES.

11. Parasite is transmitted in water (free-swimming and cyst stages), or by falling off of an infected fish (even one that seems healthy because of 9.). This means that water OR fish from another aquarium can carry the disease to another aquarium.

12. The parasite can infect bony fishes, including eels, sharks, and rays, though many species of fish, like Mandarins, have a good resistance to MI, they can still be infected and can harbor or carry the parasite. Invertebrates, snails, crabs, corals, plants, etc. are not affected/infected by MI, but the MI can be in their water, shells, etc.

13. There is no such thing as a dormant stage for MI. The parasite can’t wait around for another host. It MUST go through its cycle. Dr. Burgess recorded that in the cyst stage, he found the longest existing cyst to last for 60 days before releasing the free-swimming parasites. This is rare but possible.

14. INTERESTING FIND: If no new MI is introduce into an infected aquarium, the MI already there continues to cycle through multiple generations until about 10 to 11 months when the MI has ‘worn itself out’ and becomes less infective. A tank can be free of an MI infestation if it is never exposed to new MI parasites for over 11 months.