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Getting Rid of Ich on Fish and Aquariums

White spot disease, or ich, is caused by infestations of the parasite Ichthyophthirius multifiliis on fish.

By Stephen M. Meyer |

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Q. I have a 55-gallon goldfish aquarium — or at least I had one. I had two beautiful orandas, two bubble-eyes and one lionhead. About a month ago, some of them began to show white spots like salt specks on their skin. They sometimes darted around the aquarium, rubbing against things. Then, they got quiet and died soon after.

The guy at the pet store said it was ich. I used the antibiotic tablets he sold me, but they did not seem to help my goldfish at all. I want to start over, but first I need to disinfect my freshwater aquarium. I was told to use chlorine bleach and to scrub everything: glass, ornaments and gravel. When will it be safe to put fish back in it?

A. It sounds like ich to me, too. Often called white spot disease (because the parasites on the skin look like white spots), it is caused by infestations of the parasite Ichthyophthirius multifiliis.

Before I describe how to disinfect your freshwater aquarium, I want to help you understand a bit about this parasite and how it becomes a problem. Ich is one of those fish parasites that is always present on goldfish to some small degree, and it is ubiquitous to the fish aquarium environment. Given a fish aquarium with five or six fish, I can always find a few individual ich parasites. Healthy goldfish can easily keep these organisms under control, so they do not become a disease problem.

However, when goldfish health begins to decline (that is, when they get stressed by poor water conditions, overcrowding or poor nutrition), their ability to control ich declines quickly, and the parasite multiplies. In an unhealthy aquarium — and especially in an aquarium where one or more fish are especially weak - the parasite population will explode and infect all the fish.

Thus, before getting any new fish, you need to figure out what went wrong in this aquarium. Was the pH outside the nominal range of 6.5 to 7.8? Were there ambient levels of ammonia and/or nitrite in the water? Was there insufficient aeration? Is there chlorine in your water? Find out why your goldfish were so weak and susceptible to ich before you add new fish.

You can use chlorine bleach to disinfect everything, but it will also destroy the biological filter in your aquarium. Then you will have to restart the nitrogen cycle, and either wait two months until the aquarium stabilizes or sacrifice more fish to ammonia and nitrite and risk rekindling an ich outbreak all over again.

There is a better way. Empty the aquarium of fish. Drain the aquarium of water and refill it. Restart the filter and add a little household ammonia to feed the biological filter — just enough to reach 0.5 ppm using an ammonia test kit. Raise the fish aquarium water temperature to 75 degrees Fahrenheit. Let the aquarium run for about 10 days. If there are ich parasites still in the aquarium, they will be unable to find a host and will die. Similarly, any eggs will hatch and the parasites will die off. End of story.

You can add new fish after the incubation time passes. First, completely change the water again. Test pH, ammonia and nitrite. Return the water temperature to normal.

Before bringing new fish home, examine them with a magnifying lens while they are in a plastic bag to be sure they are not already infested with ich. Do not buy fish that are listless, float in odd ways or have visible disease signs.

After you add the new fish to the aquarium, use a malachite green-formalin parasiticide to treat the aquarium as per the instructions, which should recommend three successive treatments three days apart. Essentially, your aquarium is serving as a quarantine aquarium.

Keep testing the water every other day for a week, then once weekly. If you maintain healthy aquarium water conditions, you should not have an ich problem again.

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Reader Comments

Mrfreshwaterfish    Chicago, IL

12/20/2013 7:48:07 PM

Not a good article. Failed to address several factors. (1) Ich Is a protozoa parasite not a bacteria, therefore antibiotic does not work. (2) For Ich, methylene blue + formalin should be used. (3) Raising the temp to 85 or higher should also occur to speed up ich metabolism and life cycle (faster metabolism=faster absorption of medication. To start the aquarium over, just raise the temperature to 88 degrees, and let it sit empty for 2 weeks. Ich needs a host to live. Within 2 weeks without a host, Ich will naturally die (just make sure temp is 85 or higher to ensure complete life cycle). Messing with ammo0nia and bleach (both are very toxic)done by the average aquarists will kill fish off very fast. Poor advice in my opinion.

Dot    Hawk Junction, ON

4/16/2012 4:13:15 PM

Great advice.

Jay    Campbellton, NB

2/20/2012 3:17:21 PM

I had a fight with Ich and won but lost 1 Neon Tetra before i noticed it was present in my tank. Then i noticed my male Guppy, my 2 German Blue Rams and 1 other Neon Tetra were showing signs of it (little white specs on them) so i immediately raised the temp to 88.F sometimes a little higher and added a tsp of salt to every 5G on water changes. If you want to help the poor fish out quickly to get those nasty white specs off of them take your net and catch them in it and wave it around the tank so they freak out and try to get out... by doing this they rub up on the net and it completely cleared all 4 of them from the white spots. Its not a cure but it definitely helps them recover a little better. Hope this helps

Kendra    Gillette, WY

12/13/2011 6:37:24 PM

Hello. I have a question. How do you know if your fish are getting better? I have been doing the treatments since Saturday and its Tuesday and they dont seem to be getting better. It lookes like they are shedding is that supposed to happen? PLEASE HELP!!!

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