Saltwater ich are found in nature and normal, healthy fish commonly carry a few of these parasites when collected. Left in the ocean, fish will experience no real ill effects from ick unless some other stressor is present---for instance an injury to the fish. Once captured, however, stressors to fish are extreme and the fish become vulnerable to parasitic infestation. Also, the parasite has a “captive audience” so-to-speak within the confines of a fish aquaria. Thus, while ich is a parasite that causes little trouble in the wild, it becomes a menace in the captive environment.
Most find that there is no effective treatment for ick as long as the parasites remain embedded in the fish; some, however, purport that FW dips are an effective initial treatment of ick [while the parasites are embedded in the host fish] to be followed by other, longer term conventional treatments, such as hyposalinity or copper treatment. The standard treatment for ick is hyposalinity or use of copper. My preference is hyposalinity without any sort of FW dips, as these dips are quite stressful to fish.
Ick has a life cycle of approx. 23 days during which time the parasite undergoes 3 stages. In the tomite [free-swimming] stage, the parasite is infectious to fish. During this stage, the tomite’s goal is to find a host fish, or die trying. After they attach to the gills or body of a fish, they develop into the second stage, the parasitic trophont. During this stage they burrow into the fish, feeding on it’s tissues, which can cause considerable damage and even result in a secondary bacterial infection on the infected fish. Once well fed the trophonts stop feeding and develop cystic coverings. This becomes the inactive tomont stage and during this final stage the cysts may stay trapped in the mucus of the fish, or fall off and sit on the bottom of the aquarium substrate, rocks, etc. Within 6 to 10 days hundreds of new tomites emerge looking for fish hosts and the cycle begins all over again, and again and again until something is done about it. Once ick is an active presence in the aquaria, having infested fish, it must be irradiated or it will always pose a threat to fish, and to any new fish introduced. The standard treatment for Ick is copper sulfate and hyposalinity. Only in the free-swimming stage are these 2 treatments effective.
