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Understanding and Treating Aquarium Fish Ich

Waking up one day to see freshwater ich in fish is a real icky experience. But it is one that almost every fish keeper has to deal with one day. 

Ichthyophthirius multifiliis

Ich (Ichthyophthirius multifiliis) is one of the most common aquarium fish diseases around. It is contagious, rapid spreading, and can come back even after you’ve cured a fish of the illness. 

Ich is also misunderstood; some aquarists think it is a bacteria or viral infection. When in reality, ich fish disease is a different sort of disorder. So what are the white spots on goldfish or your betta and how can we cure them for good?

What is Aquarium Ich in Fish Disease?

Ick on fish is the result of infection by Ichthyophthirius multifiliis, a protozoan that attacks the skin. It is a parasite that does not have any intermediary hosts – meaning it does not spend part of its life cycle inside of snails, worms, or other organisms. As a fish-specific parasite, ich can’t be spread to humans, either.

The ich organism feeds on cellular fluids and living cells near the point of infection. As it grows under the skin, it forms visible white dots on fish scales and skin. 

Aquarium Ich Life Cycle

As common as aquarium fish ich is, the disease is not well understood by fish keepers. So let’s take a moment to understand the life cycle and what it means for treating the disease.

The white specks on fish that you see are called trophonts. Each trophont is home to an ich parasite that is growing by feeding on your pet. How fast the trophont grows depends on the water temperature. 

Seeing a trophont develop from start to finish over the course of a week is normal. But sometimes they can develop and burst in as little as 48 hours.

What’s important to understand when treating fish ick is that the ​​trophont form is immune to almost all treatment. The trophont is covered by the fish’s own skin and mucus and won’t respond to any medication.

The idea is to get the trophonts to burst as soon as possible. When this happens the ich parasite becomes a tormont, which is a free swimming organism. Tormonts are part of the reproductive phase – a phase that is vulnerable to treatment with medicine.

Over time the tormont swells with theronts which are infectious cells that burst their way free. These theronts then seek out a fish to continue the ich fish disease and form new white spots on their skin. These free-swimming theronts are the most vulnerable form to being killed by medications.

Fish don’t develop immunity to ick and can be reinfected as long as the disease persists in your aquarium. Ich can also become chronic, forming trophonts that burst under the skin and spread the infection further. This is rare but sometimes fatal to an infected fish.

What Does Ick Look Like on Fish?

Ich forms small white bumps on fish that look like table salt. Sometimes the bumps can grow larger as in the chronic form. The bumps may start to merge and form larger theront grains.

In this video a licensed aquarium fish veterinarian provides examples of what white spot disease fish look like:

Symptoms of Ich on Fish

Ick on fish is one of the easier diseases to identify. The main symptom is little white spots that are the size and color of grains of salt. 

It looks just like someone came by with a salt shaker and sprinkled your fish. Ironic given that salt is a key remedy against the disease.

The number of white spots on fish varies. You may just see a few on a small Tetra Fish. But if your goldfish has white spots and is quite large, there might be hundreds to thousands of ich clusters visible.

  • White spots on fish the size and color of grains of salt
  • Clamped fins
  • Loss of appetite
  • Increased slime coat production
  • Scratching against aquarium decorations
  • Listless swimming
  • Eventual death

How to Cure Ich on Fish

Ich is frightening to look at and can reinfect fish time and time again. But it is still one of the easier aquarium fish diseases to cure. Medications work very well as long as you know when and how to use them.

How to Cure Ich on Fish

Medications for Fish Ich Treatment

There are dozens of brands of ich medication on the market. The cheapest are solutions of Malachite Green or Methylene Blue. Malachite Green is a dye used not just for paper and fabrics but also staining cells for microscopy.

It is popular for treating not just aquarium ich but also fish egg, body, and fin fungus. Many blends also combine it with formalin.

Methylene Blue is another biological dye used to treat parasites and fungal infections. It is safer than Malachite Green if you have invertebrates in your tank and is popular with marine reef aquarists. 

Both medications can be added right to your aquarium as they won’t kill the beneficial bacteria in your filter. You can move infected fish to a quarantine tank if you don’t want to move your invertebrates. 

But remember that the life cycle of ich means that there will still be infectious forms in your tank, waiting for fish hosts to return. 

Treating Ich in Fish with Medication

When using any medication for betta fish white spot disease you will need to remove the activated carbon from your filter. Carbon filter media does an excellent job of removing not just proteins and amino acids but medications as well. 

If your media is a few weeks old then it may be too saturated to be effective. But fresh media will suck up any ich medicine you add.

Along with your medication of choice you should increase the temperature of your aquarium water. Fish are endothermic, meaning their metabolism is regulated by the heat of their environment. 

By raising the tank temperature you will give their immune system a boost. Heat also speeds up the life cycle of the ich parasite, pushing them faster towards their more vulnerable forms.

How to Cure Ich Naturally

Some aquarists don’t like using medication to treat ich. You can use the following “tonics” to treat ich in fish. But I recommend using these alongside medicine for the fastest cure.

Using Aquarium Salt to Treat Ich in Fish

The ich organism is sensitive to salt levels in your aquarium water. Salt won’t kill it outright – at least not unless you want to risk killing your fish with too much salt. But it helps weaken ich enough that the medicine, heat, and the immune system of your fish can do their job.

You will need to use aquarium salt, not table salt, which has iodine, anticaking agents, and other additives. One tablespoon per two gallons is a typical tonic dose. You can lower this to one tablespoon per five gallons if you know your aquarium inhabitants are salt sensitive.

Make sure you research the salt tolerance of your freshwater fish and plants. Because not all of them handle even small amounts of salt. Livebearers, Cichlids, and Goldfish all respond well to salt treatment. 

Loaches, Corydoras, and Tetra Fish are sensitive to even small amounts of salt. They are also sensitive to medications as well. Since they have small scales – or no scales – they sometimes absorb fatal amounts of medication even if you follow the proper dose. It’s best to half the dose when treating these fish.

Aquarium shrimp handle salt very well. But aquarium plants can be stressed or even killed by aquarium salt. Varying salt tolerance is another reason why moving the sickest fish to a quarantine tank is a good idea.

Last, remember that salt does not evaporate from your water over time. It is removed when you perform water changes. So any water you add to top off the aquarium should be free of salt. Just add salt to water lost during water changes if you intend on continuing the ich treatment.

Ich and Water Temperature

The ich parasite’s life cycle is also affected by heat. Warming a fish tank speeds up the process of moving from the medication-immune form (white spots on fish) to the vulnerable free-swimming phase.

Increase the temperature to as high as your fish can handle. The range is 80-86°F, depending on the species of aquarium fish.

Ich and Water Temperature
Bad Mans Tropical Fish

What if I Have White Spots On Fish Not Ick?

Fish can form white spots for reasons other than ich fish disease. For example, if you see white spot on betta fish head this can be due to excess mucus or other issues. Bacterial infections can also form white spots on the head or body.

When people ask me why does my goldfish have white spots, the first thing I think of isn’t ich. I think of breeding tubercles. These are white bumps that look a lot like ich. 

They form on the head, gill covers, and face of male goldfish when they are in a mood to breed. Female goldfish sometimes develop a few tubercles as well. These white spots on goldfish are harmless and go away on their own. 


Fish ich is a disease we all have to deal with one time or another. But it responds well to treatment when you catch it in the free swimming stages. Since it won’t respond to treatment as visible white spots, you may need to treat the tank for a few weeks. 

But remain diligent and use additional methods like heat and salt. By doing so the disease will be eradicated from your aquarium.

Frequently Asked Questions About Ich Fish Disease

If this is your first time treating ich in fish then you might have a few more questions this guide did not cover. So here are a few frequently asked questions I get about fish disease ick.

Can Fish Survive Ich Without Treatment?

Fish ick does not go away on its own without treatment most of the time. The water volume of an aquarium is so small that the parasitic load is high compared to natural bodies of water. Ich parasites will reinfect your fish again and again. If you see ich symptoms in your fish it is best to begin treatment right away.

What Causes Ich in Fish?

Fish ich is caused by a protozoan organism. The parasite can penetrate fish skin and feed on cells and fluids. Over time the parasite swells, forming visible white spots on the skin. 

Can Humans Get Ich From Fish?

Ich just infects aquarium fish. It is also an aquatic organism. So there is no chance of aquarium ich spreading to humans and infecting you.

Jason Roberts
About Jason Roberts
Jason is an aquarium fanatic that has been a fish hobbyist for almost three decades.