Ich (ick or “white spot”)

1.1.11. Ich

Fish in a newly set up aquarium often get little white spots all over their bodies. This is a disease called “ich” or “white spots”. Treating ich is very easy. Just use formalin/malachite green (Ich-X, Rid-Ich Plus, Blue Planet White Spot Remedy, and Mardel QuickCure) to treat ich in freshwater fish.

Below I get into ich in more depth than I like. But there is a huge amount of misinformation out there. Easily 80% of the advice on social media is just well meaning but wrong. So there has to be more discussion than I would like for an introductory discussion.

Ich on an Oscar
Ich on an Oscar

Summary for White Spot or Ich

MYTHBUSTER: ALL the well-done scientific studies by researchers on heat and ich have found heat to be totally ineffective in treating ich!

Note there are two other diseases that look like ich (tetrahymena in livebearers and epistylis in other fish). So make sure you have ich.

Public Aquariums use formalin/malachite green (Ich-X, Rid-Ich Plus, Blue Planet White Spot Remedy, and Mardel QuickCure) to treat ich in freshwater fish, as do University Research Centers, Cory of Aquarium Co-op, and Joey.


  • NEVER turn off the filter, remove the filter, change the filter media or clean the filter media. If the carbon has been in the aquarium for more than two weeks do NOT remove it (contrary to some directions). This is VERY important.
  • Do NOT move the fish to a quarantine tank (contrary to some directions).
  • Formalin and malachite green are both toxic in large enough dosages so carefully follow the dosage directions on the medication bottle.
  • If one raises the temperature with formalin/malachite green the medication can become somewhat toxic.
  • Cory and others have treated thousands of “scaleless” fish with full strength formalin medication with absolutely no problem.
  • Formalin/malachite green is not poisonous to snails or shrimp at the proper dosage.
  • At 76 degrees formalin and malachite green need to be added every day to be effective.
  • Follow the directions on the medication as to water changes.
ich, ick or white spot disease on Ancistrus
ich, ick or white spot disease on Ancistrus

The seminal study on ich treatments (Tieman and Goodwin, 2001) found salt (0.25%) and heat to have no effect on ich. Other studies say 0.5% to 1% salt can reduce mortality from ich but is not as effective as medication. UV sterilizers, even at low wattages, can help immensely to eliminate ich from the aquarium.

Established filters have thousands of little carnivorous critters in them which eat the infectious ich stage (the “theront”), so the filter is very important. The net result of this filter “medication” is that if you have a long-established aquarium filter with plenty of brown “gunk” in it, it is perfectly OK to do absolutely nothing for the ich. It will simply go away on its own in a week or two.

Because ich will go away in an established aquarium, there are at least 55 “treatments” currently “absolutely guaranteed” to stop ich.  There is an old saying in science: “correlation does not imply causation”. ANY treatment of ich in a tank with an established filter will work. The ashes from the cremation of a dead squirrel will work to remove ich in a tank with an established filter.

Ich on a Tetra
Ich on a Tetra

Ich in a Little More Depth

Ich is the most common aquarium fish disease that is easily recognized (fish TB is much more common but doesn’t cause symptoms during most infections). Ich is a disease that is commonly encountered by newcomers to the hobby. So an article for newcomers on ich seems appropriate.

Ich is a disease that looks like a fish that has had white salt grains sprinkled on it. The white spots MUST be small, the same size as a grain of table salt, and no larger. If the spots are larger it is not ich but rather epistylis or tetrahymena. Epistylis and tetrahymena mimic ich and pictures of these two diseases are commonly labeled “ich” by all the well-intentioned commentators on social media. Another characteristic of ich is that the white spots of ich are everywhere on the fish. Epistylis and tetrahymena occur in patches.

Ich is rarely fatal in an aquarium with an established filter with a lot of brown gunk in it. But a new tank with a new filter that hasn’t built up some brown gunk can have fish fatalities with ich. So I always recommend beginners get some Ich medication with their new aquarium. Treating ich is very easy. Just use formalin/malachite green (Ich-X, Rid-Ich Plus, Blue Planet White Spot Remedy, and Mardel QuickCure) to treat ich in freshwater fish. 

Various Fish with Ich
Various Fish with Ich

Ich in Far More Depth

For a far more in-depth analysis of ich click on this link:

10.2.2. Ich in far more depth

Startpage Aquariumscience

Source: Aquariumscience.org – David Bogert

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