I figured I'd start a discussion on Ich, in Marine fish. The reason I'm doing this is because there's a lot of myths and mis-information, regarding Ich, in Marine Fish, as apposed to Ich in Freshwater fish. I figured some of these myths needed to be "brought to light." Lately, on a couple of Reef Forums, a lot of new hobbyists have been struggling with Ich. It seems I've been reading 2 or 3 new threads every day. Unfortunately, some members are giving out bad information, which will only make matters worse. So I decided to start this thread, hoping it'll lead someone in the proper direction!!
To start with, Ich is a parasite that can infect Marine and Freshwater fish, HOWEVER, it's two totally different parasites. Some treatments for Freshwater Ich won't kill Saltwater Ich.
Marine Ich=Cryptocaryon irritans
Freshwater Ich=Ichthyophthirius multifiliis
It's important to properly identify Marine Ich, before treatment begins. Just as in Freshwater fish, Ich will present itself in a way that looks like someone sprinkled salt on your fish. It will come and go, with the Trophont, ProTomont and Tomont stages of the life cycle. Trophont is when the parasite is actually attached to the fish and usually lasts 3-7 days. After this, the parasite falls from the fish and lives in the substrate (ProTomont stage) for a period of hours. Then, during the Tomont stage, the parsite encysts, dividing into hundreds of "daughter" parasites, called Tomites. Tomites are non-infectious and this stage can last from 3-28 days. After this Tomite period, the eggs hatch, becoming Tomonts and go in search of a Fish Host.
Another interesting thing about Marine Ich, is that it seems to drop off Host Fish, AND search out Host Fish at "night." This creates a problem for the fish. Most Marine fish chose the same spot to "sleep," every night. Because of this, the Ich parasite falls off of the fish, goes through it's reproduction cycle, and easily finds the same Host Fish, when it's ready.
Here are some "treatments," that don't work.
While increasing temperature is a common, and somewhat effective way to treat Freshwater Ich, it does absolutely nothing to help with Marine Ich. There's some studies to show that it "might" speed up the life cycle of the parasite, but even these studies are controversial. Marine Ich also has a higher "optimal temperature," so raising the temperature could actually benefit the parsite. Raising water temperature also has the negative effect of lowering the oxygen content of the water.
While garlic has been shown to have immunity boosting properties, among Freshwater Fish, it has been shown to NOT have the same ability among Marine Fish. Studies have shown that garlic "may" inhibit the parasites ability to find fish, by smell, in Marine fish, so "might" result in a reduced ability to parasitize. Garlic is also thought to "possibly" increase a Marine Fish's appetite, keeping the fish healthy and able to "fight off" Ich, but even that is only anecdotal and hasn't been reproduced, scientifically, in many studies. Garlic HAS been shown to cause liver damage, among Marine Fish.
The use of a UV Sterilizer will reduce the number of Ich parasites, but not significantly. The problem with UV is it will only kill stuff that passes over the light, and ONLY if the UV light is strong enough and the life form passes over the light slow enough for the UV Strength to kill it. The Ich parasite is only in the water column for a short time, while dropping off of a Host Fish, or in search of a Host Fish. It can only pass through the UV sterilizer during the period of time that it's in the water column. Unfortunately, UV will only kill a small portion of the Ich parasites, IF the UV sterilizer is powerful enough (wattage) and the flow rate is slow enough.
Marine Ich is present in all Marine Fish and is in all Marine Tanks and is a result of a fish being stressed
A huge myth!!! Research has shown that, with proper QT procedures and treatment, Ich can be eradicated from a Marine Aquarium. Without a Fish Host, Marine Ich will die. However, the life cycle of Ich has to be taken into account, so the Ich parasite needs to be void of a Fish Host for a period of 6-8 weeks.
Now I'll outline some SUCCESSFUL treatments for Marine Ich.
Hyposalinity treatment is probably the most successful and least stressful treatment, if done properly. Unfortunately, this can't be done in a reef tank. However, it can be done in a Marine Fish Only tank, with a caveat or two.
Hyposalinity is treatment by lowering the salinity of saltwater, to a level that it will kill the parasite, but NOT kill the fish. In fact, lowering salinity eases a fishes ability to "respire," and increases oxygens ability to mix with the water.
Changes in salinity do need to be done correctly, as to not stress the fish. Lowering the salinity can be done quicker than raising the salinity. Typically the salinity can be dropped from 1.025 to 1.009 in a matter of a couple of days, without negatively effecting the fish. However, once treatment is over, the salinity should be raised back up to 1.025 slower (over the period of a week.) Treatment needs to be done for a period of 6-8 weeks, OR at least 2 weeks after all visible signs of Ich are gone. At that point, salinity can be slowly raised, over a 1 week period. During this same time, the display tank must remain "fallow," or fishless. Without any Fish Hosts, the Ich parasite will die.
1.009 has been shown to be the level where Ich can no longer survive, without negatively effecting the fish. Again, this cannot be done in a reef tank, as motile and inmotile inverts will die. In a Fish Only system, this can be done, however, beneficial bacteria, micro fauna, micro flora, amphipods, copepods, etc. will perish. Those things will re-populate, over time.
Hyposalinity is best done in an established QT tank.
Copper treatment CANNOT be done in a reef tank and shouldn't be done in a FO (Fish Only) Tank. The copper will leach into the live rock, sand substrate, etc. Later, the copper will leach back out of these materials, poisoning the tank. Copper is very fatal to any Marine Inverts.
Copper treatment needs to be done very carefully and with a very accurate Copper Test Kit. At too low of dosage, it won't kill Ich. At too high of dosage, it kills fish. It's very important to follow the manufacturer directions AND have an accurate test kit.
This method is effective, but a lot of work...lol.
It involves having 2 available tanks. Each day, the fish are moved from one tank, to another. In between, each tank is emptied, cleaned and refilled with Saltwater. The idea is that the Ich parasite will be left behind, in the used water. This process should be done for a period of 10 days. This treatment is also quite stressful to the fish, with being moved every day. Also, the display still needs to remain fallow for 6-8 weeks.
Here's some further reading, for those interested.
Marine Ich/Cryptocaryon irritans - A Discussion of this Parasite and the Treatment Options Available, Part I by Steven Pro - Reefkeeping.com
Garlic: What has been Studied Versus What has been Claimed by Steven Pro - Reefkeeping.com