There are a few freshwater ich treatment options you can use in your aquarium.
Q. In my 55-gallon aquarium, I have many ghost shrimp that I think may be going through a bout of ich. Do you know of any ich medications that wouldn't hurt them?
A. Ich is a common protozoan that attacks fish and is visible as tiny white dots on the fish's flesh where the parasite digs in. Ich is easy to treat, but the disease can be lethal if left untreated. Ghost shrimp can't catch ich, but because they are often kept in aquariums with fish, and because some ich medications can be lethal to invertebrates, one must be careful choosing a treatment.
You'll find scads of ich medicines in stores, but they all use the same few ingredients. Nearly all ich medications are safe enough for use with ghost shrimp, but your safest bet is a plain malachite green medication.
Malachite green, sometimes listed as Victoria green or aniline green, is effective against ich, and it is safe — although some fish are more sensitive to it than others. Most brands tell you to use half a dose for tetras and scaleless bottom fish. I have never found malachite green — properly dosed — to bother any fish, plants or any invertebrates kept in freshwater aquariums.
Another advantage of malachite green treatment is that it does not deteriorate water quality, so there is no need to do extra water changes during or after treatment (although you may need to do a change before treatment). Poor water quality is one major stressor that can make fish susceptible to ich. Always run water tests to be sure the environment is correct before medicating.
Malachite green is a stain that gives the water a bluish tint, but the color normally dissipates within a couple of hours. This compound may stain the silicone rubber seams of your aquarium, but I have not found it to do so excessively. It may stain some ceramic decorations, as well.
Remove activated carbon from your filters during treatment — the carbon will adsorb the medication before it ever has a chance to work. Detritus will also absorb some of the medication, so if your aquarium is dirty, use a gravel vacuum to give the substrate a quick cleaning before medicating the aquarium.
Formalin and formalin/malachite green remedies are also sold. Formalin is stronger than malachite green and kills more types of organisms, but it's rough on plants and water quality, and is a bit rougher on invertebrates, too (it also messes with the readings of some ammonia test kits). So, it would not be my first choice with ghost shrimp. Partial water changes are necessary during and after treatment with medications containing formalin. Formalin/ malachite green combos are said to be synergistic (stronger and safer when used together), but you're still left with the necessity of extra water changes.
Acriflavine is another common ich medication. This chemical looks a bit mustard brown when the concentrated drops first hit the water but appears fluorescent green as the medication disperses throughout the aquarium. This medication works and should be safe for shrimp and your freshwater fish, but to get the color out of the water after the treatment, plan on making a large water change and using fresh activated carbon in your filter.
Metronidazole is sometimes offered as an ich treatment, but it tends to be more expensive. It doesn't color the water, but water should be changed after treatment, anyway.
Although there are a few more ingredients used to treat ich, we'll close this discussion by talking about copper sulfate. Copper medications can be lethal to invertebrates, and should never be used with ghost shrimp. Happy fishkeeping!