The Dreaded Ich: Treatment, Prevention, and Causes

Reading Time: 8 minutes
ich fish disease

Ich, Ichthyophthirius multifiliis, or “white spot disease” is one of the most common illnesses that you’ll run into – so how do you cure it? You know what they say: “To know your enemy, you must become your enemy.” While it might not be practical to create a machine that turns you into a fish-gobbling parasite, I can give you the lowdown you need to get inside the head of this familiar foe.

Ich comes from a protozoan parasite (Ichthyophthirius multifiliis), and the white spots you see on your fish are your fish’s immune system reacting to the parasite – not the parasites themselves. But I’ll talk more about that in a minute. 

Although most consider battle white spot disease an unpleasant nuisance or a common byproduct of keeping fish – it can be extremely damaging to your fish. Not only does it tax your fish’s immune system, but it can result in damaged gills, slow suffocation, ulcers, skin loss, and death in fish with weak immune systems.  

Oddly enough, it seems as though Ichthyophthirius multifiliis can be easier to cure in some fish than others. German blue rams, for example, seem to always have it no matter how many times you treat it. It’s challenging to treat in coldwater fish like goldfish since heat is an essential factor in treatment.

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Table of contents

ich white spot disease



  • Small white spots 
  • Fish itching or scratching against rocks, décor, or gravel 
  • Lethargy
  • Lack of appetite 
  • Redness or bloody streaks on the body and fins

You’ll often see you in ebb and flow pattern in these symptoms as it goes through its life cycle. You may even find times were it looks like the ich has cured itself only for it to come back more prominently than ever.  It’s also worth noting that just because you don’t see white spots, doesn’t mean ich isn’t there. If you see your fish scraping and scratching against rocks – also called flashing – it could be ich before their body reacts to it or it could be such a mild case that white spots never appear. (Remember, white spots are their body’s reaction to ich, not ich itself.)


We already know Ichthyophthirius multifilis (a protozoan parasite) is responsible for ich. But where does it come from? And why do some fish get it while others in the same tank are totally fine?

  • Stress: stress plays a major role in immune system responses. When fish (or people, or any living thing, really) are stressed, their immune system is suppressed. This is a perfect opportunity for all sorts of things to creep into their body. 
  • Stress can come from improper tank mates, bullying, the wrong water parameters, too much light, not enough hiding places, not enough friends, too many “friends” for fish that are solitary. It can even be you just stare at the tank too much. 
  • Undeveloped immune system: this is the case when fry come down with ich.
  • Newly Introduced fish: a newly introduced fish is, not only stressed but likely stresses out established inhabitants as well. This is a prime opportunity to introduce a pathogen. 
  • Newly introduced plants: although rarer, pathogens can come in on any surface that was in an infected tank – including plants. 

Even with those things out of the way, ich is so widespread that the chances your fish haven’t come into contact with it are incredibly slim. 

Ich Life Cycle

Ich has a somewhat complicated life cycle that often confuses people. I think the majority of the confusion comes down to terms like trophozoites, trophont, and tomites, which all look relatively similar (and a little eye-glazy.) But it’s an essential topic for understanding how to treat ich.

ich fish disease

Trophozoites (Ich You See On Fish)

Trophozoites attach to the skin or gills of the fish and mature there. While these buggers are gnawing on the skin and tissue of your poor fish, your fish’s skin becomes irritated. As a result, their immune system encysts the ich in a white dome-like bubble.

This white “bubble” is what you see when your fish has ich – but it isn’t ich itself, just a reaction to the ich. The bubble limits the damage ich can do to the surrounding tissue, but it also makes the trophozoites impossible to kill since medications can’t penetrate this bubble.

Once mature, the trophozoites will burst from this bubble and will be called…

trophont ich

Trophont (“Reproductive” Ich)

Trophonts leave their protective fish bubble to fall to the floor of your aquarium – or any spot they land. This stage is where the “adults” (trophonts) will divide into hundreds of baby ichs, more or less. (Although scientists would likely frown and call them tomites.)

This stage is incredibly temperature-dependent. Trophont division happens fastest between 79 – 80F (26C), and this stage can complete in as few as eight hours in that range. At lower temperatures, replication happens slower, and the time to finish treatment is, as a result, more time-consuming as well.

Once replication is complete, the trophont will burst and release hundreds of tomites into the water.

ich tomite

Tomites (Free-Swimming Ich)

Tomites, once released, will swim around to find a fish to attach to. But they’ll rest on plants, decor, in the gravel – basically, anywhere they see fit. At this stage, ich is easily transferred from tank to tank. However, while it’s most contagious, it’s also easiest to kill.

Tomites can only survive for 48 hours without a host to feed on, but they can’t seem to attach at temperatures of 86F and up (30C.) Some medications kill tomites, and a few other methods you could utilize at this point, but I’ll cover that in a second.

Once the tomites attach to fish, they become trophozoites, and the cycle starts over again.

Depending on the water temperature, the whole cycle can take a few days to weeks. There is no hard and fast answer for how quickly they’ll go through their life cycle.

Treating Ich

There are a few methods you can use to treat ich, but before we get to those, I suggest you follow these steps first for any plan of attack:

1. Water Change:

Unless you literally just changed the water – like today – I would advise you to change it. There are a few reasons why but, for one, your fish will likely sit in the water their in for a few days if you add meds to their water. Two, it helps get rid of some of the free-swimming and “adult” ich that are left in your tank, hopefully reducing the number in your tank out the gate.

2. Add Air:

Start pumping some air into the tank now since your water is currently at a lower temperature, and it will hold oxygen better.

If you can saturate the tank as much as possible before raising the temp, your fish will have an easier time breathing once it gets hotter. Trying to do this the other way around is much more difficult (and less effective.)

3. Increase Temperature:

Temperature increases help speed up the life cycle of ich so you can kill them faster. The max, if you can, would be 89F (31C), but if you can get your temp up to at least 86F (30C), that should be high enough. If you have cold-water fish like goldfish, or if your fish are less heat resistant you can take your temp up as high as you (and they!) feel comfortable going.

Slowly bring your temperature up by one or two degrees every few hours – you don’t want to shock them. The same is true for bringing the temp back down (but more on that in a minute.)

Treat Ich Using Heat

aquarium thermometer

At 86F (30C) there is some indication that ich either a.) cannot reproduce or b.) cannot attach itself. Either way, if your fish can tolerate those temperatures (up to 89F or 31C) temperature increases might be a viable option for eradication of ich without medication.

It’s worth noting, however, that I’ve attempted this method with hit-or-miss results. Sometimes ich will seem to “fix itself” at this temperature and disappear after a few days, other times it makes the situation worse.

If you want to attempt this method, bring the temp as high as your fish are comfortable going. Providing your fish can go higher than 86F, leave the temp there for four days and bring it back down to 86F for two weeks to be sure they’re all gone. If you notice it’s making the problem worse, switch to another method below.

Treat Ich Using Salt

aquarium salt

When medication is not an option (which is common with sensitive fish), you can use salt in combination with heat to treat ich – though you need to proceed slowly with this method.

It’s advised to add two to three teaspoons of aquarium salt per gallon. You can mix this solution is a one-gallon jug and slowly add the brine solution over a few hours. Just be sure to monitor for stress in the fish over this time. If you’re feeling crafty, you can hook the jug up to an irrigation dripper (or make your own) where it will slowly drip into the tank, no extra work needed on your part.

It’s worth noting that this method is, obviously, not suitable for tanks with snails or most invertebrate species.

Treat Ich Using Garlic

ich garlic guard

Garlic helps boost the immune response of many animals, and fish are no exception. You can add Garlic Guard to your fish’s food a few times a week to help boost their immune system to help fight off ich. This method is probably not appropriate for severe cases of ich, however.

You can also make a DIY form of garlic guard, but it takes about a day according to most recipes.

DIY Garlic Guard Directions:

  1. Separate bulb into cloves and snip off ends.
  2. Microwave cloves for five to ten seconds to pop hulls.
  3. Remove hulls
  4. Cut the cloves into thin slices
  5. Place in a (covered) cup of hot water and let sit for 12 hours.
  6. Once done “marinating,” mash the cloves and strain.

You can use this mixture immediately and store in your refrigerator for two weeks.

Treat Using Medications

ich X

First, remove your carbon if you’re going to do this and follow the directions on your package. Some ich medications include malachite green, methylene blue, quinine hydrochloride, copper, and mepacrine hydrochloride – or any combination of those. It’s crucial if you have shrimp to check for copper in the medication to avoid killing your inverts.

I prefer to use a single dose of Ich X and leave it for a week without water changes. I change the water after a week and dose again if I feel like I need to. I’ve never had any issues with this method (including with shrimp or snails.) But use whatever process makes you feel most comfortable.

Preventing Ich

Ich isn’t entirely avoidable, but you can significantly reduce the risk of infestation if you follow a few precautionary steps:

1. Quarantine new fish and plants:

Quarantining won’t avoid the need to cure ich with some newly acquired fish, but it will significantly reduce the risk of infecting fish you already have as well as make it easier to cure ich. A properly set up quarantine tank should be bare (no gravel, no plants, etc.) And while it may seem above and beyond to quarantine new plants, if you purchased your plants from a tank with fish in it, this step is entirely necessary. Just because you don’t see ich on the fish in the tank, doesn’t mean it’s not there.

2. Avoid using wet equipment on more than one tank:

Even if your tanks are healthy, avoiding using wet equipment on more than one tank is an essential step in preventing cross-contamination. This includes nets, siphons, pumps, heater, plants – basically anything. Wait a few hours for it to dry out before you put it in a new tank.

3. Reduce live food use:

Unless you culture your own live food, in which case, disregard. But if you frequently buy feeder fish, blackworms, bloodworms – or any other live food – it’s best avoided until you can culture your own. This prevents a ton of the risks associated with live foods. Avoiding live food may be nearly impossible with obligate piscivores that are difficult (or impossible) to get on a frozen food diet – but these instances are rare in home aquariums.

Further Reading & Resources

Science Daily – ‘Ich’ discovery could yield new ways to treat devastating freshwater fish parasite

Aquaculture – Ich (White Spot Disease)

Science DirectIchthyophthirius-multifiliis

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