Causes, Symptoms & Treatment Of Ich On Fish – Freshwater Aquariums

Ich (pronounced ick) is one of the most common diseases in tropical fish aquariums. It's something you will have to deal with if you keep fish for any amount of time. I know it’s stressful, but don't panic, it's actually quite easy to deal with if it's caught and treated early.

As ich can wipe out every fish in your tank if left untreated, it’s vital you learn how to identify it and deal with it immediately.

I’ve successfully treated ich outbreaks many times over the years and you can too. Thankfully I’ve learned from the mistakes I made in my early days of fishkeeping, and very rarely have to deal with ich these days.

This post will cover the most frequently asked questions about ich on fish.

What Is Ich?

Ich, also known as white spot disease or ick disease, is a parasitic infection in freshwater fish caused by the protozoan parasite Ichthyophthirius multifiliis. It is an opportunistic organism that takes advantage of your fish when their immune system is suppressed.

Ick on fish presents itself as small (up to 1mm / 0.04 inches) round white spots attached to your fish’s body. You will typically see small white spots appear on your fish’s fins first which will quickly spread to the rest of their body, but not usually around their eyes.

Ich on fish Clown Loach
Ich on clown loach

Each spot feeds on your fish’s skin and tissue, before dropping off, multiplying, and releasing up to 1,000 infective theronts into your aquarium. These new theronts look for a host fish to attach to and the process repeats over and over until you treat it.

Signs Of Ich

Signs & symptoms of ich include:

  • Increased respiratory effort is an early warning sign of ich. One of the first things ich targets on your fish is their gills, which makes it more difficult for them to breathe
  • White spots on the body, fins, and gills
  • Flashing – flattening themselves out at the bottom of the tank and rubbing against the substrate or decor, twitchy swimming, sudden bursts of swimming, or even jumping out of the water
  • Bruising or scale loss – this will be a sign that your fish has been flashing
  • Loss of appetite
  • Appearing lethargic
  • Hiding more than normal
  • Fins clamped to the body
  • Pale coloration
  • Every fish in your aquarium dies suddenly

Does My Fish Have Ich?

Just because your fish has white spots on its body doesn’t necessarily mean it has ich.

If you notice 5 white spots on your fish today, and 15 white spots on your fish tomorrow, then you’re more than likely dealing with ich. If you see 5 white spots today and 5 white spots tomorrow, chances are it’s not ich.

There are other causes of white spots too such as epistylis, fin ray fractures, or lymphocystis.


Epistylis can easily be confused with ich to the naked eye. It is localized to a certain area of the fish, to begin with, but will eventually spread across the whole body including the eyes. Ich covers the entire fish’s body evenly but rarely around the eyes.

An epistylis spot is translucent whitish-grey in color with a varied shape and size and can look like small tufts protruding from the body. An ich spot is a clearly defined white spot, around the size of a grain of salt.

Fin Ray Fractures

A fish’s fins are made up of cartilage and webbing. If they bump into the tank sides, tank decor, or other fish, this cartilage can be broken and white spots will form around the break to hold it in place.

Usually, these white spots will form a straight line and cannot be scraped off by your vet, unlike ich, lymphocystis, or epistylis.


Lymphocystis spots clump together near the fins, whereas ich is evenly distributed across the whole body. Lymphocystis quickly turns from a white spot to a pinkish cauliflower-like growth.

Identifying Ich

Vet identifying ich
Vet identifying ich

The best way of identifying ich in fish is to consult your vet. They will take a scraping of a white spot and examine it under a microscope. It’s very clear to a vet whether your fish has ich or another disease.

I have left details of where you find a specialist fish vet in your area at the bottom of this post.

What Causes Ich In Fish?

The No.1 cause of why fish get ich is not quarantining new fish, invertebrates, or plants before adding them to your display tank.
It only takes a single ick parasite to wreak havoc in your aquarium, it’s just not worth the risk of not quarantining new additions.

Keeping your water parameters at the correct levels is vital. If they’re out of whack it can stress your fish and leave them vulnerable to ich.

Overstocking (having too many fish in your tank) is a sure-fire way to screw up your water parameters due to the increased bioload placed on your aquarium.

Watch out for any fish that are getting bullied by other tankmates, this will lead to your fish becoming stressed, thus more susceptible to getting ich.

Other causes can include:

  • Using infected equipment between tanks without sterilizing them thoroughly
  • Transferring infected filter media between tanks
  • Moving infected decor between tanks
  • Not washing your hands and forearms thoroughly between tanks

Is Ich Always Present In Aquariums?

That’s a hotly debated topic in the fishkeeping world. Many experts in the hobby believe that because it’s so common it may be present in your aquarium all the time and your fish build up an immunity to it.

But should something happen, like a sudden change in water parameters, for example, your fish become stressed and this lowers their immune system allowing the ich parasite to take advantage.

My own view on this is I assume it’s always there lying dormant waiting for an opportunity to breakout. As I don’t want to have to deal with it, it keeps me on my A-game when it comes to taking care of my aquarium.

How Do You Prevent Ich On Fish?

Quarantine new fish and invertebrates for 4-6 weeks before introducing them to your display tank.

This gives enough time for any disease or infections to appear and allows you to treat them appropriately without infecting your main tank.

I know you are excited and want to add your new fish to your tank right away – but patience is key when it comes to preventing disease!

Quarantine new plants for 4 weeks with no fish.

Ich (and many other diseases) need a host fish to survive, so if you quarantine new plants for 4 weeks with no fish you will break the parasite’s life cycle.

Make sure to fertilize your plants over this quarantine period so they are in tip-top shape when you add them to your display tank.

Provide your fish with enough hiding places. Some fish like to be out in the open, some like to hang out under plants and rocks to feel relaxed. You need to set up your aquarium according to their needs.

Spend time with your fish and learn what their normal behaviors are. You’ll be able to spot anything out of the ordinary which could be an early warning sign of ich.

As always, maintaining good water parameters and feeding your fish a high quality diet will help prevent most issues.

How To Treat Ich On Fish

When treating ich, you need to treat the entire tank, not just an infected fish. This disease spreads super fast so you need to assume that if 1 fish is infected, your entire tank is infected.

I always have a bottle of ich medication to hand as it’s crucial to start treating ich as soon as possible.

You don’t want to be rushing out to your local fish store only to find they’re out of stock or your preferred medication and then have to wait for delivery.

Ich Life Cycle

To treat ich successfully, it’s vital that you understand the life cycle of ich:

Stage 1 – Infective Theront – The theront attaches to the fish and feeds off its skin and flesh, eventually becoming a mature trophont.

Stage 2 – Mature Trophont – The trophont detaches from the fish and drops onto the tank’s substrate or plants where it becomes a reproductive tomont.

Stage 3 – Reproductive Tomont – The reproductive tomont bursts open and releases up to 1,000 infective theronts into the water, they then look for a host fish to attach to and the cycle starts from stage 1 again. 

Ich Life Cycle
The life cycle of ich in freshwater fish

The length of the life cycle is temperature dependant, the higher the water temperature the shorter the life cycle.

The entire cycle from attaching to the fish to releasing the infective theronts is approx 6 days at 75-77°F / 24-25°C.

Ich is impervious to any form of treatment during stages 1 and 2 of its life cycle.
You can only kill ich off during stage 3 when the infective theronts are free-swimming and looking for a host fish to attach to.

Treating Ich With Medication

What is the best ich medication? Having tried out most ich medications on the market over the years, I’ve found Ich-X by Aquarium Solutions to be the best treatment you can buy and it’s the only ick medication I use nowadays.


It’s fish, plant, and invertebrate safe, just follow the instructions on the label:

  • Add 5ml of Ich-X per 10 gallons of water per day
  • Perform a 30% water change before adding the next dose

A couple of pointers for Aquarium Solutions Ich-X:

  • Remove any activated carbon from your filters and clean or replace your filter media. Any organisms trapped in your filter media will absorb the treatment and stop it from working. Do not stop tank filtration.
  • One of the ingredients in Ich-X is malachite green, it may stain things in your aquarium green, I’ve not had any issues with this, but some people have found it stained their silicone.
  • It will stain your clothes or carpet should you spill any, I speak from experience here. Let’s just say the wife wasn’t best pleased!!!

Treating Ich With Salt

API Aquarium Salt

Adding aquarium salt to your tank is another way to treat ich, but you have to make sure your fish can handle the extra salt content in the water.

If you have catfish, plecos, loaches, snails, and plants in your tank, these are all sensitive to salt so I recommend skipping straight to the medication treatment method.

The ich parasite doesn’t survive well in water with a salt content of 1 part per 1,000. That equates to 1 tablespoon of aquarium salt per 5 gallons of water. Some fish like African cichlids, guppies, and mollies can tolerate double that concentration.

Aquarium salt has a few benefits besides combating the ich. It helps the fish control the amount of water content in its body, which helps repair the outer tissue that the ich has fed off. It also aids the repair of the fish’s protective slime coat layer which helps keep ich and other bacterial infections at bay.

Do not use regular iodized table salt or marine salt in a freshwater aquarium.
Table salt contains additives that are harmful to fish.
Marine salt is a completely different type of salt.

Treating Ich Naturally

I always treat ich with meds as I find it’s the most effective solution, but if you don’t want to add chemicals to your aquarium there’s a natural method you can try, but only IF your fish and plants can handle it.

Raise Your Water Temperature

Gradually raising your water temperature to between 83-84°F for a few days will speed up the life cycle of the ick parasite.

However, this has the knock-on effect of lowering the levels of dissolved oxygen in the water, making it harder for your fish to breathe. Adding a couple of air stones will help increase oxygen levels.

Be aware if you have goldfish or other cool-water fish, raising the water temperature too high will kill them.

Reduce Aquarium Lighting

Reducing the amount of time the lights are on will allow your fish more R ‘n R time. If you felt poorly, could you be bothered with bright lights or would you rather crawl under a blanket and recuperate? Fish are the same.

Feed Less Food

Chances are if your fish is suffering from ich it won’t be eating as much food as normal. Any leftover food is just going to sit on the substrate and rot, increasing the bioload in your tank.


There are a lot of people online who claim to have treated ich with garlic, however, there are no scientific studies that prove garlic is effective at treating ich.

Garlic may help boost the health and immune system of your fish so it may help prevent ich outbreaks in the future and it can be useful in helping stimulate your fish’s appetite.

What Next?

Once the last sign of ich has gone from your tank, keep medicating for at least another week. Remember, ich is only vulnerable in stage 3 of its life cycle, so you have to be 100% certain it’s gone.

Imagine going through this entire process, stopping treatment, and in a couple of days’ time, you notice a white spot on one of your fish! You’ll be right back at square 1 and have to start all over again!!

If you’re using the temperature and salt method keep it up for a further 2 weeks.

For cool water fish like goldfish, I’d keep going for up to a month. The cooler your water temperature the longer ich’s life cycle is.

Once you’re certain the ich is gone, you’ll need to sterilize any nets, pipes, and siphons that you’ve used in your infected aquarium to minimize the risk of cross-contamination and infecting another aquarium. If you think ich is a pain in the butt to treat in 1 tank, try having an outbreak in multiple tanks!!

I have a 5-gallon bucket set aside for this task and I use a 10% bleach solution:

  • 1 quart of bleach to 2.5 gallons of water

I let everything soak in the bleach solution overnight before rinsing them thoroughly and letting them air dry for 2 weeks. Any ich virus leftover cannot survive the 2 week drying process.

Can Ich Affect Humans?

Thankfully not, I’m not aware of any humans ever being infected with the ich parasite.

Find a Fish Vet Near Me

It’s always advisable to consult your local vet. If you would like to seek veterinary advice you can find a specialist aquatic vet in your area using the links below:

Closing Thoughts On Ich On Fish…

Although ich is very common in aquariums, it doesn’t have to be a death sentence for your fish if treated quickly and properly.

I hope this guide has put your mind at ease and you now know how to identify the early signs of ich on fish, deal with it effectively, and prevent it from re-happening.

Check out the Aquarium Health section for more guides just like this one and keep your fish tank in tip-top shape.

Picture of Paul


Hey, fellow fish enthusiast 👋! I'm Paul and I've been an aquarium addict since I won my first goldfish at the fair many years ago. Let me share with you the knowledge that I've gained along the way (and avoid the mistakes I've made!), so you too can create an underwater paradise for your aquatic friends.