"Ich", or "White spot disease", is a primarily cutaneous infection of freshwater fish caused by the protozoal parasite Ichthyophthirius multifilis.
Ich most often causes the appearance of small white spots over the body and fins of fish. However, it is important to note that ich can present with many different appearances, and that other things besides ich can cause small white spots on the body. Thus, the only sure-fire way to know that what you're treating is ich is to scrape the skin of your affected fish and look at the scraping under the microscope.
For those of you interested in looking at things under the microscope, Ichthyophthirius is a large ciliated protozoan with a U-shaped macronucleus. Its shape changes as it moves through the water, and it appears to "tumble" as it moves. (You can mail me for more detailed instructions on skin scrapings etc. if interested.)
For those of you not interested in skin scrapings, you can have a high rate of success just assuming that what you're treating is ich.
To effectively treat ich, it's important to understand a little bit about the life cycle of the organism.
-------> ADULT (on fish) ------- | | | | | | TOMITE TROPHOZOITE | | | | | | ------------- CYST -------------
The adult stage lives on the skin and body of the fish. It will burrow under the epidermis, causing skin damage. Disruption of the skin leads to osmoregulatory disturbances, osmotic stress, and allows for the easy entrance of secondary invaders like bacteria.
The cyst stage lives on the bottom of the aquarium, and gives rise to about 300 tomites per cyst.
The Tomite stage is the only stage which is sensitive to medication!
The life cycle takes 12-16 days to complete, depending on the temperature, and the tomite stage lasts for only three days.
All of these facts may seem trivial, but they are important because they dictate what treatments will be effective.
How to Treat ICH (The Important Stuff)
1. Check your water quality!!!!!! 9 times out of 10, the fish can do fine with a few Ichthyophthirius in the water, but when they are stressed by anything, like questionable water quality, it makes it much easier for the little buggers to set up shop in your fish's skin.
2. Do a 50% water change, just to be safe.
3. Add 3 tsp of aquarium salt per gallon to your tank. This reduces the osmotic stress on the fish caused by the invading organisms, and may adversely affect the organism as well.
4. Pick up an ich medication of your choice at the local fish mart. Most of the ones that are sold are more or less effective. My personal favorite is a malachite green/formaldehyde combination sold under the brand name "Quick Cure". ("RidIch" has the same ingredients.) Note: Most people recommend halving the dose of Malachite-containing medications if you are treating small catfish, any scaleless catfish, or tetras.
5. Disregard the instructions on the bottle!!!!! Use the DOSE written on the bottle, but treat like this: Treat every 3 to 4 days for 4 treatments, changing 50% of the water before every treatment. Do NOT treat once or twice, like the directions will tell you! You need to treat over 12 to 16 days in order to get all the little guys when they are vulnerable. (See life cycle diagram for explanation)
(Excuse the digression here, but this is my chance to vent my frustration at the aquarium trade -- I think they purposefully give poor medicating information so that the consumer will treat only partially, and knock down the parasite burden only enough to temporarily cure the fish! Because not all the organisms are dead, they will bounce back in a few weeks or months, and the poor consumer has to run out and but more of the ich medication! What a scam!!)
Other things which may help:
6. Raise the temperature in the tank above 85 degrees for 5-7 days. The tomites do very poorly at these temperatures, and it also speeds up the life cycle so more organisms are vulnerable to killing at any time.
7. You can use a diatomaceous earth filter to decrease the number of infective tomites.
8. Move fish to a clean tank after 7 days. This reduces reinfection by tomites left behind after the initial treatments.
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