This is probably the most common of the saltwater fish diseases that hobbyist can experience. It's very important that the aquarist learns quickly to recognize the parasite and correctly treat it. First and foremost what the hobbyist needs to realize is that Ich is a parasite and not a disease. Cryptocaryon irritans infections usually progress much slower than Amyloodinium, though it can be just as deadly. If the fish are carefully observed on a daily basis, the telltale white, salt-size spots should be apparent before the infection gets out of control. Usually, some of the fish appear unaffected at the onset. Common names include the following: White Spot Disease and Saltwater Ich.

Some symptoms to look for are as follow:
• White spots about the size of a pin head or grain of salt. The parasite is usually noticed on the skin and fins first, and later the eyes.
• Usually only some, but not all, of the fish are affected until the disease has progressed for at least a few days.
• Spots seem to be gone but come back again after a few days.
• Some fish scratch but not as often or violently as seen with Amyloodinium infections.
• Shuddering, flashing or twitching
• Hyperactivity in early stages
• Increased breathing rate
• Increased mucus production
• Faded colors
• Cloudy eyes associated with secondary bacterial infections
• Staying near the surface or in areas of high water flow
• Lack of appetite in advanced stages
• Hiding
• Fin rot or other secondary bacterial infection in late stages

What causes marine "Ich"?

Marine "Ich" is caused by a ciliated protozoan called Cryptocaryon irritans Brown 1951. Ciliates (Phylum Ciliophora) are one of the largest groups of protozoans and all posses cilia or compound ciliary structures for food acquisition or locomotion at some point in their life cycle. Of the some 7200 species that have been described, around one third are ecto- and endo- commensals and parasites (Ruppert and Barnes, 1994). C. irritans is an obligate ectoparasite (Dickerson and Clark, 1996) which means that it is an external parasite that needs the fish host to complete its life cycle. The name 'Marine "Ich"' has been coined because it is essentially the marine equivalent on Ichthyophthirius multifiliis Fouquet, 1876, or "Ich" for short. While the two species of ciliates have superficially similar life cycles and signs, they have been found to be only distantly related (Wright and Colorni, 2002) .

The life cycle stages of C. irritans

C. irritans has a four stage life cycle, as shown in Figure 1. The parasitic stage (trophonts) is the one that results in the appearance of white spots all over the fish. The trophonts burrow under the skin where they feed on body fluids and tissue debris. When the trophonts first infect the fish they are small but grow as they feed and so the white spots are initially small but get larger as they mature. Once mature, they drop off the fish and sink/swim down to the substrate where they encyst and begin to reproduce. In this stage they are called tomonts. After a number of days in which the tomonts divide, the cyst ruptures, releasing the tomites. Tomites may differentiate into theronts, the infective stage, which actively seek a host to reinfect.



Treatment

There are only two proven methods for the treatment of Marine "Ich", copper and hyposalinity. Neither method can be used in the presence of elasmobranchs (sharks and rays), corals or invertebrates, so if you have any of these in your display tank, then the treatment must be performed in a quarantine or hospital tank. Hyposalinity is the preferred treatment as it is not dangerous to the fish and actually eases osmotic stress on the fish. Hyposalinity only works on Ich, so you need to be sure you have Ich before you start to use it. Also you shouldn't use Hyposalinity with live rock. For a more detailed description and method of hyposalinity, please see Ich Part II.

Copper is toxic to both fish, corals and invertebrates and must be used with care. Copper should not be used in the presence of corals, invertebrates or elasmobranchs. Copper is not very stable in sea water and the levels must be continuously monitored, so a good test kit is very important. It's very important to treat at the correct levels, as too little doesn't work and too much can kill a fish. General you should treat at .25ppm for 2 weeks, after you see the last spot on a fish. In general 4 weeks is a good treatment period.

There are other methods for the treatment of marine "Ich", but, generally, they have limited success. One of the problems with assessing treatment methods for marine "Ich" is that fish may recover through acquired immunity, which gives the impression that the treatment was effective when perhaps the fish would have recovered on their own.

It is worth noting that many people have had apparent success with adding garlic to the food of infected fish. Garlic is well know for its therapeutic effect, particularly in humans and it is possible that the same active ingredients may be effective in fish, too. The theory behind the use of garlic is to strengthen the fish's immune system's, also the garlic is suppose to make the fish's skin taste bad, so that the Ich wouldn't attach to it, basically it repeals the Ich. As with other treatments, it is difficult to assess the effectiveness of garlic, as the fish most likely would have gotten well on its own and it had nothing to do with the garlic. still, garlic seems to get and keep fish eating, which is important as the fish is fighting off the Ich.

Another good thing is to keep the lights on, or a light on near the tank. This keeps the fish activity and strong, as it fights off the Ich.

Prevention

The best prevention of keeping Ich out of your display tank is to quarantine all your fish for 4 - 6 weeks, the longer the better before you place them into you display tank. In that time you should see signs if the fish has something, and if it does, start to treat it. However, you shouldn't treat a fish until you know what the fish has, and at that point treat with the correct medication. So you shouldn't treat a fish with copper or hyposalinity, or any medicine, before you know what it has.

Are freshwater dips effective?

Freshwater dips are generally ineffective in the treatment of marine "Ich" infestations. Trophonts burrow deeply into the epithelium where they are generally protected from external influences. Colorni (1985) found that even after 18 hours in freshwater, infected fish still have trophonts attached in the same positions as they had held before the freshwater treatment. The trophonts later detached and completed their life cycle as normal. Trophonts penetrate the epithelium which causes a loss in osmoregulatory capability. Infected fish are less able to cope with a sudden and drastic change in the ionic concentration of their environment. This is likely to cause further stress to the fish which will impair their ability to acquire immunity to the parasite.

Hyposalinity is a very effective treatment for parasitic conditions such as Marine "Ich" (Cryptocaryon irritans.) and can also be used to lower stress in fish.
What is Hyposalinity?
Hyposalinity is adjusting the salinity of the water to somewhat less the that of natural sea water. For the treatment to be effective the salinity needs to be lowered to 12-14‰ which is equivalent to a specific gravity of 1.009 (d20/20) at normal tank temperatures (26-28°C - 79-82°F). Normal sea water has a salinity of 35‰ (Gross, 1977).

How does it work?
For the treatment of "Ich", hyposalinity works by breaking the life cycle of the parasite. The lower salinity may also reduce stress, although there is no hard evidence to date to support this. C. irritans is a ciliate protozoan found in sea water and it has a number of stages in its life cycle. Infective stages burrow into the skin and gills of the fish and form a protective outer covering of skin. Here they feed on tissue fluids and skin and grow. When mature, the parasite breaks out of the cyst and after some time as a free-swimming form encysts on any suitable substrate such as the sand or rocks and divides many times to produce the infective forms (Colorni, 1987). The infective forms must find a suitable host or they will die.

The total time from the mature parasite detaching from the fish and reinfection of the fish is about 2 weeks at normal tank temperatures. This is why "Ich" may appear to clear up but then comes back a a week or so later but a lot worse. The low salinity causes the most of the tomonts to rupture, killing them Marine teleost fish (higher bony fishes) maintain their osmotic concentration at about one quarter to one third that of sea water. In normal sea water, these fish have a tendency to lose water from their gills due to osmosis and also in their urine. Fish have to drink a lot of water to make up for the loss, however, as the water contains a lot of salt (35‰) they must remove the excess salt from their system. The sodium and chloride ions are secreted by the gills and magnesium and sulphates are excreted in urine. This is an active process and requires energy much like the energy required to keep warm blooded animals warm.
When fish are under stress, one of the processes that is affected is ion regulation. This means they have difficulty adjusting the concentration of ions (sodium, chloride, etc.). Lowering the salinity of the tank water makes the concentration of ions closer to that of the fish"s internal fluids and reduces the fish"s efforts to maintain the correct concentrations.
Please note that only the higher bony fishes have lower osmotic concentrations and can be treated this way. Marine invertebrates have the same osmotic concentration as the surrounding water (Schmidt-Nielsen, 1975) and if left in the aquarium during hyposalinity treatment are most likely to die due to osmotic shock. Sharks and rays may not survive hyposalinity due to their unique method of osmoregulation. They have similar concentrations of salts to that of marine teleosts (one quarter to one third that of sea water), however, they also have very high concentrations of organic compounds which gives their internal fluids the same osmotic concentration as sea water. While some can adjust to lower salinities, most will succumb to osmotic shock just like invertebrates.

Where do you treat?
The first choice you must make is whether to treat in the main display tank or in a quarantine tank. The main display tank can be treated if it is "Fish Only" and contains no invertebrates or live rock. The live rock itself will survive the treatment, but any invertebrates living on and in it will be killed. If the tank is truly "Fish Only" treating the tanks is probably the best option as there will be less stress to the inhabitants and it helps you to eliminate the "Ich" in the main tank. If the main display tank is "Fish Only With Live Rock", it may be possible to move the live rock to another tank and treat the main tank, but in most cases and when the tank is "Reef" tank, removing the fish to a quarantine tank is the only option. At that point you want to leave the display tank empty of fish for 6 - 8 weeks, at which point the Ich will have died off, as it wouldn't be able to find a host to live on.

When a quarantine tank is to be used, it is wise to fill the quarantine tank with water from the main tank when the fish to be treated are moved. This will help reduce the stress of the move and alleviate the acclimation process. It may still be necessary to acclimate the fish if time has passed from when the water was transferred and the fish are transferred.

How do you treat?
It is very important that you can accurately measure the salinity or specific gravity of the water. Cheap hydrometers, especially the swinging arm variety, do not have enough accuracy. If the salinity is too high, it may have no affect on the parasites, as discussed above. A refractometer is the safest method for measuring salinity. The goal is to granularly reduce the salinity of the water to between 12 and 14‰ and leave it at that salinity for at least 4 weeks but preferably 6 weeks. Basically continue the treatment for at least 4 weeks after the last spots disappeared. The salinity must be lowered gradually to give the fish time to adjust to the lower salinity and more importantly ensures the bacteria in the biological filter can adjust. It should take around 2 days to get from 35‰ to 14‰. Your starting point should be between 1.025 and 1.027. Replace about one fifth of the volume with RO, RO/DI or aged freshwater that has been well aerated. Repeat this 12, 24 and 36 hours later, monitoring the specific gravity along the way. After the fourth water change the specific gravity should be 1.010 or pretty close. Wait a few hours to make the final adjustment to get down to 1.009. Note that you can estimate the resulting specific gravity. If you are changing one fifth of the water and the current specific gravity is 1.025 the result will be:

• ((1.025*4)+1.000)/5 = 1.020 approx.

Then, after 12 hours:

• ((1.020*4)+1.000)/5 = 1.016 approx.

After 24 hours:

• ((1.016*4)+1.000)/5 = 1.013 approx.

After the 4th change:

• ((1.013*4)+1.000)/5 = 1.010 approx.

Water temperature influences specific gravity and if you heat water without changing the salinity the specific gravity will decrease. As the goal is to keep the salinity between 12 and 14‰ it is important to know the temperature as well as the specific gravity. What temperature should you use? Some people have argued that raising the temperature is good because it speeds up the life cycle of the parasite. While this is true, the elevated temperature also raises the metabolic rate of the fish causing increased oxygen and energy consumption and somewhat negating the benefits of the hyposalinity. Temperatures close to "normal", those the fish are used to, will be the best. Ensure the temperature is taken into consideration for the specific gravity.

While the fish are being treated it is extremely important to closely monitor the pH and specific gravity. Unless you are treating in a well established tank with an established biological filter there will be a tendency for the pH to drop and this must be monitored. This can also happen in an establish tank due to the lower salinity. If the pH starts to drop, water should be changed or buffer very carefully added to the system. If the fish are sick, too rapid changes in pH will not be beneficial. The specific gravity also must be monitored as excessive evaporation will cause the salinity to rise and possibly create suitable conditions for the free swimming parasite. If the salinity does rise, it may be necessary to extend the length of the treatment after the salinity has been lowered again. For this reason I like to drop the salinity to 1.008.

Hyposalinity should be maintained for at least 4 weeks but 6 weeks is preferable. If there is any reinfection of the "Ich" during the treatment, the treatment should be extended to at least 4 weeks after you see the last white spot on the fish.

When the treatment is complete, the salinity should be raised gradually to normal over a number of days. Water changes with normal or even high salinity water is the easiest way to get the salinity up. Calculations using averages, as before, can be used to determine the appropriate specific gravity of the replacement water. If you replace one sixth of the 1.009 water with water at 1.025, the specific gravity will be raised to 1.012:

• ((1.009*5)+1.025)/6 = 1.012 approx.

As the salinity approaches normal it will be necessary to either replace more water in each change or use water with a higher than normal salinity. If you have been treating in a quarantine tank, you will need to leave the display tank with no fish in it for at least 6-8 weeks. This will ensures that all remaining parasites in the tank have gone through their full life cycle and the infective forms have died. If you have been treating in the display tank, you should wait some time before returning any invertebrates or live rock to ensure that the biological filter has had time to adjust to the salinity and load.

Warnings
Corals, Invertebrates, sharks and rays cannot tolerate low salinity and should be removed from the tank.

• Temperature affects specific gravity and must be considered.
• Ph can drop during treatment and must be monitored.

Summary

• Isolate the fish from any coral, invertebrates or sharks and rays
• Lower the salinity to 12-14‰ (specific gravity: 1.009 @ 27°C) over a 72 hour period
• Closely monitor the Ph and specific gravity
• Do regular water changes with low salinity water
• Keep the salinity at 12-14‰ (specific gravity: 1.009 @ 27°C) for 4-6 weeks, or at least 4 weeks after the last disappearance of the "Ich".
• Raise the salinity to normal over a 3-7 day period.
• Leave an untreated display tank fishless for at least 6-8 weeks.

Copper Sulfate Treatment (For Treating Fish-Only Tank & QT)
A copper sulfate treatment is the most effective treatment for both Oodinium and Cryptocaryon. Copper is NOT invert, coral, live rock or reef safe, and some fish are copper sensitive, such as scaleless species, and they should not be exposed to it either. Copper should not be used in a saltwater aquarium unless it is a fish-only tank, and intended to stay that way.

Once copper sulfate is introduced into a tank it cannot be completely removed. The level of copper sulfate to be effective is at .25 ppm. Be sure to not let the copper level fall below .25 ppm, otherwise, it will not work and the Ich problem will continue on. Keep the fish under treatment for at least two weeks, four is even better, after the last theronts has fallen off the fish body.

Very important, get a good test kit, as if you treat at too low of a level, it will have no effect, and too high, will kill the fish.



Is "Ich" always present in our aquaria?

There is a widely held belief in the marine aquarium hobby that "Ich" is always present in our aquaria. There is much information in the scientific literature that contradicts this belief.

C. irritans is an obligate parasite (Burgess and Matthews, 1994; Dickerson and Dawe, 1995; Yoshinaga and Dickerson, 1994). Obligate means the parasite can not survive without infecting its host, in this case, fish. Theronts have been shown to die if a suitable host is not found within the required time. Yoshinaga and Dickerson (1994) found that few theronts (0.34%) were viable 12.5 hours after excystment and Burgess and Matthews (1994) found that no theronts were viable 18 hours after excystment. Colorni (1985) found that some excysted tomites (=theronts) were observed to be moving weekly after 48 hours. While the life span of the theronts appears variable, it is limited and all will die without finding a suitable host.

If an aquarium has no fish in it or anything else that could be carrying trophonts, tomonts, tomites or theronts for a period of 6 weeks or longer, all parasites will have died. An aquarium such as this is an obvious exception to "Ich" always being present theory.
Many fish collected for marine aquariums will not be carrying "Ich". Incidence of C. irritans in wild fish varies widely and may be geographically related. Some authors have found few infected fish, if any, in the areas they have examined (Puerto Rico: Bunkley-Williams and Williams, 1994; southern California: Wilkie and Gordin, 1969) . Others have found that low levels of infection are not uncommon (e.g. southern Queensland; Diggles and Lester, 1996c). Keeping multiple fish in holding tanks and at aquarium stores increases the chances of a fish carrying "Ich" parasites, but it is still possible to acquire a fish that is not infected with "Ich".
If new fish are quarantined for at least 6 weeks, any parasites on the fish will have gone through a number of life cycles increasing the number of parasites present. In the majority of cases, the increase in parasite numbers will result in full blown infection and fish can be treated to remove the parasites. Hyposalinity has been demonstrated to break the life cycle of "Ich" (Cheung et al. 1979; Colorni, 1985) and fish correctly treated with hyposalinity will be free from "Ich".

If fish that are free from "Ich" (either because they were not originally infected or because they have been treated with hyposalinity) are added to an aquarium that is free from "Ich", the aquarium will stay free from "Ich" and be another exception to "Ich" always being present, theory.
Burgess and Matthews (1994) were attempting to maintain a viable population of C. irritans which could be used in later studies. To maintain the parasite populations, they needed host fish in order for the trophonts to feed and continue the life cycle. Each host fish was only used once in a process of serial transition such that none of the hosts would die or develop an immunity. While the procedure worked very well and enabled them to maintain populations for some time, the viability of the populations decreased with time and none of the 7 isolates they used survived more than 34 cycles, around 10 to 11 months. They suggest this is due to senescence and aging in cell lines is well recognised in Ciliophora.
The presence of aging cell lines in C. irritans suggests that an aquarium that has been running for longer than 12 months without any additions is unlikely to have any surviving "Ich" parasites, yet another exception to "Ich" always being present theory.

While "Ich" may be present in some tanks, it is certainly not present in all tanks. Through careful quarantining and treatment, it is very possible to establish and maintain an "Ich" free aquarium.



Does stress cause "Ich"?

Stress and poor water conditions do not cause marine "Ich", although they will lower a fish's resistance to infection and impair their immune system. If Ich is not present in a tank, it doesn't matter how stressed a fish may be, it cannot get infected. In a tank where parasites are present, stressed fish are more likely to show signs of "Ich" before more healthy fish, but the healthy fish are just as likely to become infected as the numbers of parasites increase. Those fish species that are less susceptible to "Ich", or those individuals that have an acquired immunity, may show no signs and may not get infected.

Can "Ich" be introduced with natural seawater?

One common argument against the use of natural seawater is the possibility of the introduction of parasites. While it is theoretically possible to introduce C. irritans, it is practically very unlikely owing to the nature of the life cycle of the parasite.
As discussed above, C. irritans spends very little time in the water column. After dropping off the host fish, trophonts head straight to the substrate to reproduce. This may take as little as 30 minutes but could extend to 24 hours (Cheung et al., 1979). Burgess and Matthews (1994b) found that significantly more trophonts left their host during darkness while fish are resting. This would greatly decrease the chances of trophonts being swept away from the substrate. These two factors combined almost rule out the possibility of trophonts being collected with natural seawater.
Excystment of theronts from tomonts also happens at night (Burgess and Matthews (1994b) and as theronts are only viable for a few hours, the chances of collecting theronts is low and those collected will most likely die before use in an aquarium.

Can "Ich" be introduced by corals, live rock or sand?

It's very possible to introduce Ich to your display tank by adding live rock, corals or live sand from another tank that may have Ich.

UV & Ozone Sterilization Units
Many people choose to run UV (Ultra Violet) or Ozone Sterilization units. These units only destroy the Ich during the new born, free swimming life cycle stage of the parasites. They do not kill or remove the Ich parasites once attached to the fish. UV & Ozone sterilization units can assist in controlling an Ich bloom from getting out of hand, but will not eliminating the problem all together, as the free swimming Ich needs to go through the UV unit. Because of this, not having all the free swimming Ich going through the UV unit, UV aren't something that can rid a tank of Ich.

Naturally Susceptible Fish
There are many fish species like Tangs/Surgeon Fishes that seem to be easily prone to contacting Ich, ICH MAGNETS. For example, if you are familiar with the Achilles, Goldrim, Hippo and Powder Blue Tangs. You can choose to avoid fishes that are known to be prone to coming down with Ich or heavily quarantine them before placing them into you main tank.