Why does my fish have white spots?

Aquarium owners know the joy of a thriving tank – fish gliding gracefully, colors shimmering under the light, plants swaying gently in the water. Every aquarium owner, from beginners to experienced keepers, can encounter health issues with their fish from time to time. One of the common health issues I hear all the time is the dreaded White Spot Disease or “Ich”.

This guide will help you understand what White Spot Disease (Ich) is, how it spreads, and how to treat it can make all the difference in saving your fish and restoring harmony to your aquarium.

So, what is White Spot Disease (Ich)

White Spot Disease, commonly referred to as Ich or Ichthyophthirius multifiliis, is a highly contagious parasitic infection that affects freshwater fish. It’s one of the most recognisable illnesses in the aquarium world, marked by tiny, salt-like white spots on the body, fins, and gills of the fish.

Ich is caused by a protozoan parasite that attaches to a fish’s skin, feeding on the host and causing tissue damage. Left untreated, the disease can lead to severe stress and secondary infections and can even lead to death so it is important to act fast.

It is a tough protozoan – it can survive in temperatures ranging from 1 to 30°C, but as a thermophilic species, it requires temperatures above 15°C to reproduce quickly and efficiently.

Figure 1: Fish Ich under a microscope – Scanning electron microscope image of Ichthyophthirius multifiliis (Photo: Ole S. Møller, University of Copenhagen)

It is important to understand the Life Cycle of Ich

Understanding the life cycle of the Ich parasite is vital for effective treatment. This parasite goes through several stages:

1. Trophont Stage (Feeding Stage): This is when the parasite becomes visible as white cysts on the fish. During this stage, the parasite feeds on the fish’s tissues, causing damage and visible white spots. Treatments are typically ineffective at this stage.
2. Tomont Stage (Reproductive Stage): Once mature, the parasite falls off the fish and encysts itself in the substrate or other surfaces in the aquarium. Here, it begins to reproduce, dividing into thousands of new tomites.
3. Theront Stage (Free-Swimming Stage): The new, free-swimming parasites, called theronts, search for a new host. If they do not find one within a few days, they die. This is the stage where the parasite is most vulnerable to treatments.

The complete life cycle of Ich can be affected by water temperature, with higher temperatures speeding up their lifecycle stages.

Signs of a Fish Suffering from White Spot

Being able to identify the signs of White Spot Disease early can make a significant difference in your fish’s recovery. Here’s what to watch for:

• White Spots on the Body and Fins: The most obvious sign is the appearance of small, salt-like white cysts scattered over the fish’s body, fins, or gills.
• Rubbing or Scratching Against Surfaces: Infected fish may exhibit abnormal behaviour, such as rubbing or scraping against rocks, decorations, or the tank walls, in an attempt to relieve itching and discomfort. This is called “flashing”.
• Laboured Breathing: If the parasite affects the gills, you may notice your fish breathing heavily or spending more time near the surface where oxygen levels are higher.
• Lethargy or Reduced Activity: Sick fish often become less active, hiding more frequently or appearing sluggish.
• Loss of Appetite: A decrease in appetite is another common sign, as the stress and damage caused by the parasite can make eating difficult.

Important Note: Some freshwater fish species like Clown Loaches are more susceptible to ich. This is because they are nearly scaleless (their scales are super thin and tiny) so it is important to catch it super early with loaches and other types of ‘scaleless’ species.

Juvenile Clown Loach with a parasitic Ich infection ☹️

If you think one of your fish might be infected, you will need to treat the entire aquarium, as Ich is highly contagious and can spread quickly from fish to fish.

One way to treat Ich is to raise the aquarium temperature slowly (between 2 to 4 degree celcius), as this speeds up the parasite’s life cycle and makes them more susceptible to treatment. Add an additional air diffuser is highly recommended because as the water temperature rises, the less dissolved oxygen there is in the aquarium. Use common sense and observe for fish that might not tolerate higher temperatures. Vacuum your substrate every day to help decrease the Ich numbers at the Tomont and Themont stages. One Tomont can produce up to one thousand daughter cells (tomites) so being vigilant with cleaning the substrate helps a great deal.

Specialised Ich medications

Specialised Ich medications are widely available in our store and, when used as directed, can be very effective. We have a range of medications that can help.

You will need to remove any carbon in your filter media because carbon removes / neutralises the medications that you put into the tank.

We recommend Ichonex by Aquasonic

It is super important to follow the directions carefully and to not overdose the tank. You can use our handy calculator on our site to measure the exact volume of your tank by just adding your tank dimensions.

The active ingredients of these medications are usually Formalin and malachite green and they are not known to be poisonous to snails or shrimp when correctly dosed.

Increase their slime coat production

Another tip is to add some aquarium salt to the tank. You can add this along with specialised ich medications. Aquarium salt can gently irritate a fish’s slime coat, which causes the fish to produce more mucus that can make it harder for parasites and microorganisms to latch on. Add 1 tablespoon (Tbsp) of salt per 19 litres of water.

How can I help prevent ich outbreaks?

Dealing with White Spot Disease / Ich can be stressful and time consuming plus no aquarium fish lover wants to witness their pet fish falling ill! A few simple precautions can go a long way in keeping your fish healthy and your aquarium Ich-free.

Quarantine New Fish: It might be tempting to introduce new fish into your tank right away, but patience pays off. Set up a quarantine (or what we call an emergency hospital) tank and keep your finned newcomers there for at least two weeks and observe for any out of the norm signs. This way, you can make sure they’re disease-free before they join the rest of your aquatic family.

Maintain Water Quality: Good water quality is essential for happy, healthy fish. Poor conditions can stress them out, making them more prone to diseases like Ich. Make a habit of regularly checking your water parameters, including ammonia, nitrite, nitrate, and pH levels. A clean, stable environment is key.

Avoid Sudden Changes: Fish can be sensitive creatures, and sudden shifts in temperature or pH can cause a lot of stress. Take care to make gradual adjustments when needed and keep your tank environment as stable as possible.

Handle Fish with Care: Rough handling can be stressful or even injure your fish, leaving them vulnerable to infection. Whether you’re netting them or doing routine maintenance, be gentle and take your time.

Can Ich spread to humans?

No, thank goodness! You will not be infected with ich if you touch a fish infected with ich or even the aquarium water. It would be a creative halloween costume though if you ever had an aquarium themed party! 

The average normal body temperature is about 37°C and it can only live in temperature conditions of up to 30°C

Proper Diagnosis of Ich

It is important to make sure you do a proper diagnosis. White spots on your fish does not necessarily represent as ich. It could be its ’more troublesome white-neck cousin, Epistylis, which you can read more about it here.

If you are not unsure if you have an ich problem, reach out to us here. We can help provide the best advice for your situation.