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Home aquariums can have a variety of problems to overcome, including the common parasite that causes saltwater ich, also known as white spot disease. Caused by a parasitic protozoa, Cryptocaryon irritans, saltwater ich is easy to identify by the characteristic white spots, around 0.5 to 1.0 millimeters in size, that typically appear on a fish's fins and skin. However, if the parasite only infests a fish's gills, the fin and skin spots may be lacking. In this instance, the main symptoms are respiratory distress, lethargy, and rapid breathing.
The best ich treatment is copper-based medication. Rather than treating the main aquarium, move the sick fish to a bare bottomed quarantine or treatment tank. This should be aerated and have the same water conditions as the main aquarium. Here are treatments to try for white spot disease.
Mardel Coppersafe, from Fritz Aquatics
Mardel Coppersafe from Fritz Aquatics treats both freshwater and saltwater ich, along with other diseases, including Velvet (Oodinium) and other external parasites. However, because it is a copper-based treatment made from chelated copper sulfate, any invertebrates in your tank must be removed before using the product. Consider removing plants and snails, too, as the medication could be harmful to them, as well.
To use Coppersafe, add 1 teaspoon of medication for every 4 gallons of water, or 1 cup of every 190 gallons. The solution will remain active in the tank for more than one month.
Cupramine, from Seachem
Cupramine, a copper-based treatment from Seachem, treats not only saltwater ich, but also other ectoparasites in freshwater and saltwater tanks. An ionic copper medication, rather than chelated copper, it is non-acidic and doesn't damage the biofilter bacteria; however, invertebrates still need to be removed from the aquarium before treating.
To use Cupramine, turn off UV filters and ozone filters, and remove chemical filtration, such as activated carbon. For every 10.5 gallons of water, use 1 mL of treatment, and then wait 48 hours. Repeat the treatment, and leave at this concentration for 14 days. Test the water for copper levels before redosing the tank.
RALLY, from Ruby Reef
If you need a copper-free treatment for saltwater ich, try RALLY from Ruby Reef. It's made from acriflavine, aminoacridine, and formalin, so it's not harmful to fish, invertebrates, or corals. However, it might not be the top treatment for C. irritans, so you may need to combine it with an alternative treatment, such as KICK-ICH—another copper-free treatment from Ruby Reef. RALLY does, however, succeed at treating other external parasites, such as dinoflagellates and flukes.
To use RALLY, remove carbon filtration and other absorbent media, and turn off protein skimmers and UV sterilizers. Use 1 ounce of RALLY per 5 gallons of water each day for three days.
If you prefer to avoid adding medication to your aquarium, try an alternative treatment for ich. Fish hobbyists often treat the parasites using hyposalinity, which means dipping the fish in a freshwater or low salinity water for a period of time. This causes the cell membranes of the parasites to rupture by absorption of water due to the decreased salinity. Reduce the salt level to around 0.35% salinity (one-tenth the strength of seawater) in an aerated treatment aquarium and add the fish to be treated. Remove the fish after three hours, or sooner if they show signs of stress. Repeat the process every three days until no more parasites are seen on any of the fish.