Cryptocaryon irritans (a.k.a. Marine or Saltwater Ich, Crypto, or just plain Ich) is one of the most common infestations which plague saltwater fish. It's easily identified by white spots which are about the size of a grain of salt (unlike Marine Velvet, which is notably smaller). In addition, the fish might be seen rubbing against objects, have a lack of appetite, or exhibit heavy breathing, possibly even progressing to frayed fins and cloudy eyes.
Watanabei Angelfish with Ich parasites, photo by seabass.
Ich is a parasite that will feed on its host fish for several days before heading to the substrate. After several hours on the rock or sand, it will encyst and divide into hundreds of potential new parasites. This noninfectious stage can last anywhere between 3 and 28 days. Afterward, they hatch and become free swimming parasites, looking for a fish to infect.
In the wild, this mass reproduction helps ensure the survival of the parasite. But an occasional parasite is typically easily endured by fish in the wild. However, in the confines of our tanks, where the fish cannot escape from the eventual hundreds, or even thousands, of free swimming parasites, an outbreak can lead to the death of the host fish. In addition, the infected fish will likely infect any other fish being held in their shared system (like retail fish tanks).
How To Treat Marine Ich
The two most common and effective remedies for curing fish of Ich are Seachem Cupramine™ and hyposalinity treatments. Cupramine is widely considered the most effective method, while hyposalinity may be the easiest on the fish. There are other medications which might also be effective, like Seachem ParaGuard™; however Cupramine is considered to be the gold standard when it comes to Ich medications.
Seachem Cupramine is a copper treatment, and is ONLY to be used in a hospital tank without calcium rock or substrate. This is because copper is especially toxic to corals and inverts. It also binds to calcium, which reduces its effectiveness, and makes the rock or sand unusable in tanks that will eventually contain invertebrates. And while Cupramine is a relatively safe form of copper for fish, it is still important to ensure you are treating with proper levels via testing (you should not to exceed 0.6 mg/L of copper). In addition, you must remove any chemical filter media from the treatment tank, and carefully follow the instructions on the label.
Hyposalinity, a procedure to reduce the level of salt in the water (hypo), is also highly effective, and is my favorite option for treating Ich. In fact, hyposalinity helps the fish conserve energy during osmoregulation and can even reduce stress. During hypo treatments, specific gravity is usually lowered to 1.009. This is easily endured by most bony fish, with the exception of seahorses, and reportedly some clownfish (which should be treated at a specific gravity of 1.011). It's safe to lower the specific gravity quite quickly, but it must be raised back to normal very slowly.
You must use a refractometer calibrated with RO/DI water to a specific gravity of 1.000 (versus using typical calibration fluid). Swing arm hydrometers are not accurate enough to ensure proper levels. Also note that hyposalinity cannot be used in tanks with live rock or sand containing worms, pods, or other crustaceans, as this will kill them, resulting in die off and an ammonia spike. However, hypo treatments can still be used if the live rock and sand is otherwise devoid of non-bacterial life. It can also be used in conjunction with other meds, such as Seachem ParaGuard.
Once all of the fish are visibly clear of Ich (which usually takes less than 7 days), you should maintain hyposalinity for an additional month, as the treatment is most effective during the parasite's free swimming stage. Afterward, the specific gravity should be slowly increased by no more than 0.002 per day.
There are numerous less effective remedies which range from UV sterilizers, to “reef-safe” anti-parasitic medications, all which may yield different degrees of effectiveness. In addition, there are even some ineffective remedies, like garlic. While I don't want to dispute the claims of these other marketed treatments, I tend to remain skeptical of their ability to completely wipe out Cryptocaryon, and personally recommend the use of either Cupramine or hyposalinity when treating your fish for Ich.
Wait It Out
While your fish are in their hospital tank, the display tank should remain fallow (without fish) for a period of six weeks. This is usually long enough for the parasite to encyst, hatch, and die without finding a host. If using hyposalinity in a hospital tank, it's possible to periodically introduce some water from your treatment tank into your fallow display tank; this might encourage the parasite to look for a host, not find one, and eventually die. However, you don't want to introduce any water containing copper into your display system.
Now that your tank is free of Ich, you will want to keep it that way by quarantining all new livestock. To avoid ammonia spikes in your quarantine tank (QT), you should transfer an established bio-filter from your main tank into the QT. In addition, adequate flow and lighting are required for your quarantine system. Live rock, coral, and other inverts can be quarantined for five weeks without a fish in the tank (which will provide ample time for the parasite's cysts to hatch and die). New fish can be observed in quarantine for five weeks as well, and treated with hyposalinity or Cupramine (and additional quarantine) if it becomes necessary.
- Pro, Steven (2003) Marine Ich/Cryptocaryon irritans - A Discussion of this Parasite and the Treatment Options Available, Part I [Online] http://reefkeeping.com/issues/2003-08/sp/index.php [Accessed 03/08/2017].
- Giwojna, Pete (2007) Hyposalinity or Osmotic Shock Therapy (OST) [Online] http://wetwebmedia.com/ca/volume_4/V4I4/hyposalinity/OST.htm [Accessed 03/09/2017].
- Bartelme, Terry D. (2007) Aquarium Fish: Applications for Hyposalinity Therapy: The Benefits of Salinity Manipulation for Marine Fish [Online] http://www.advancedaquarist.com/2007/6/fish [Accessed 03/08/2017].
- Pro, Steven (2005) Garlic: What has been Studied Versus What has been Claimed [Online] http://reefkeeping.com/issues/2005-10/sp/index.php [Accessed 03/08/2017].
- Pro, Steven (2003) Marine Ich/Cryptocaryon irritans - A Discussion of this Parasite and the Treatment Options Available, Part II [Online] http://reefkeeping.com/issues/2003-10/sp/feature/index.php [Accessed 03/08/2017].
- Pro, Steven (2004) An Ounce of Prevention is Worth a Pound of Cure: A Quarantine Tank for Everything [Online] http://www.reefkeeping.com/issues/2004-10/sp/feature/ [Accessed 03/08/2017].