Amyloodiniosis or "Marine Velvet"
Amyloodinium ocellatum is one of the deadliest and fastest-acting saltwater fish diseases that marine hobbyist are likely to see. Usually all of the fish that share the aquarium are infected to some degree. Some common names for this infection include Coral fish disease, and Velvet.

Visible symptoms are the following:
• Scratching
• Rapid, shallow breathing
• Most, if not all, fish are affected
• Hyperactivity
• Twitching or shuddering
• Reduced appetite
• Clamped fins
• Faded colors
• Hanging near the surface or in areas of highest water movement
• A fine, powdery dusting
• Secondary bacterial infection in the late stages, which sometimes manifest as cloudy eyes or raged fins
• Dehydration in late stages of infection

What causes amyloodiniosis?
Amyloodiniosis is caused by a dinoflagellate parasite called Amyloodinium ocellatum.

The life cycle of A. ocellatum
A. ocellatum has a three-stage life cycle: parasitic trophonts, encysted reproductive tomonts and free-swimming infective dinospores. The parasitic trophont attaches to the one or more epithelial cells via rhizoids. It appears that nutrients are absorbed via the rhizoids. After the trophont matures, it detaches from the host, retracts it rhizoids, forms a cyst and becomes a tomont. The tomont may divide up to 8 times producing 256 dinospores (Noga and Levy, 1995). The free-swimming dinospores seek out a fish host to infect and remain infective for at least 6 days at 26°C (Noga and Levy, 1995). Amyloodinium can complete its life cycle in under one week under optimal conditions (Noga and Levy, 1995).

Treatment for of amyloodiniosis
Copper is an effective treatment for Amyloodinium and it should be kept at 0.25 mg/L for at least 14 days, although 21 days is better to be certain of killing the amyloodiniosis. Copper cannot be used in the presence of invertebrates and treatment should be performed in a hospital tank, unless you don't plan on adding corals or inverts to the main tank. The copper level needs to be tested regularly to ensure that the correct level is maintained, as too low of a dosage doesn't work and too much can kill the fish. Copper is very toxic to the fish, so care must be taken to avoid overdose.