Illness and Disease Fish Tank Guides

White spot/Ich – Fish illness

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Fish Illness/Disease: White spot, also know as Ich.

White spot / ich / ick

White spot is a very common disease in freshwater aquariums. White spot is caused by a water-borne parasite Ichthyophthirius multifilis, and is commonly called ich or ick, for short.

The Ich parasite enters the tank, usually, on infected fish. However, it can also be transferred by plants, ornaments and equipment if it has been in an infected aquarium system.

White spot can reproduce quickly and is very capable of wiping out an entire tank, if the filtration is not well established. Ich seems to have a higher mortality rate in new aquariums and is an extremely common disease to see in new set ups.

A well established set up will very rarely see a death caused by white spot, it’s said that this is because the filtration helps to kill the parasite.

White spot is not as fatal as it gets credit for, it is often confused with Epistylis, which has a higher mortality rate.

Studies have shown that Ich has roughly a 35% mortality rate without intervention or treatment.

White spot Ich



The life cycle of White spot/Ich

White spot or Ich reproduces by cell division on the bottom of your aquarium. Inside a small cyst, a single organism of the parasite can produce thousands of infectious cells.

Once mature, these cells break out and become free-swimming. In order to survive, they need to find a host (your fish) within 48 hours.  This is fairly easy for them in the aquarium, which is why they are so difficult to stop in a new aquarium.

After locating a host, they invade the fins, skin and gills of the fish and begin to feed on it. Each parasite encloses itself in a thin layer which produces the White spot that you see on your fish.

The parasite feeds on fluids from the fish and can grow up to 1mm inside its little white capsule. If the parasite has attached itself to the fish’ gills, it can cause problems in the fish’ breathing.

Once they have grown and are matured, the parasites break out from their capsules and swim away.  This leaves open sores on the fish’ body meaning that the fish is now also vulnerable to bacterial infection through its wounds.

The mature parasite quickly forms a cyst, where it reproduces by dividing into thousands more infectious cells.

The total life cycle of the parasite lasts around a week.



Signs of White spot/Ich

The most obvious indicator of White spot/Ich is the spots themselves. They appear on the fish’ body and fins as little, uniform, raised white dots and can appear to look like grains of sand/salt stuck to the fish.  These are pretty easy to see on the body and fins, but if only the gills are infected then you may not see any at all, at least not unless it spreads.

Another common indicator is ‘flashing’. This is where a fish appears irritated and will scratch itself on tank decor or substrate, just as though it is trying to remove something from its body. Usually, if a fish is doing this it is being irritated by something, but it may not necessarily be white spot, so always check your water parameters and look for signs of another infection.

Other signs include fish being more docile than usual, maybe even refusing food.

Usually, White spot/Ich is pretty easy to see, it tends to affect the fins quite badly, which are quite thin, so lots of White raised spots on them are quite noticeable.

White spot and Ich



Treatments for White spot/Ich

As White spot or Ich is so common, there are loads of treatments manufactured to deal with it. These are usually available from your local aquarium store. Be sure to read the label and follow the instructions carefully when using any medication.

Medications containing formalin and/or malachite green have been reported to be the most effective.

Make sure that if you are using a treatment/medication to remove any activated carbon from your filter.  Activated carbon or purigen can remove the treatment from your water, preventing it from having its intended effect.

Your best weapon in a battle against Ich is a well-cycled filter. Good filtration keeps the aquarium clean, removing and killing the Ich parasite. It is rumoured that with good filtration alone, Ich will clear up after a few weeks.


There are many myths around Ich treatment that are well believed amongst aquarists:

The most common is that raising the water temperature will kill the parasite. It won’t.

The temperature required for this is reported to be 33 degrees Celsius (91-92F). This is too warm for most tropical fish to tolerate and will significantly reduce the available oxygen in the water.

Many aquarists may tell you that a temperature of 30C will kill Ich. It won’t.

If 30-degree heat killed Ich, then Ich couldn’t exist in warmer climates, but it does, in some areas it survives at up to 34C.

Medications such as malachite green become toxic at higher temperatures.

The Ich parasite can make it difficult for your fish to breath. Increasing water temperature only makes it more difficult for them.

Warmer water holds less oxygen. This means that whilst the Ich parasite steals oxygen from your fish, there is less of it to begin with, meaning even less for the fish itself.


Adding Salt to the water is another common ‘solution’ given when treating Ich. Whilst salt does have some medical value, its effect on Ich has been reported to be ‘limited’ at best.

The amount of salt required to prevent Ich from surviving is also far too high for freshwater fish to tolerate.

Salt in the water also decreases the Oxygen available. So when you combine all three, (Ich + high temp + Salt) then there is a risk that rather than Ich killing your fish, they will suffocate or die from stress.

If you are treating for Ich, then good filtration and a bottle of good quality medication are the best and only option. But……

As with all diseases, prevention is better than the cure….


White Spot Medication



Prevention of White spot/Ich

Ich is one of the most prevalent illnesses to affect ornamental fish, but it can be easily prevented.

Having a quarantine tank is a great idea in general, not only is it handy if one of your fish becomes Ill, but it’s also handy to prevent illness from entering your aquarium in the first place.

It is all too common to see fish riddled with White spot/Ich in aquarium shops. As you can imagine, in that crowded environment it spreads very quickly, so what looks like a healthy fish may also be infested with little white spots within a few days.

Adding a sick fish to your aquarium can spell disaster, so if you quarantine for a week or two in a separate tank first, you can be far more sure that new fish are healthy and disease free before adding them to your main aquarium, keeping your existing fish safer.

Maintenance is key! Keeping up with your maintenance is the key to a healthy aquarium, plus it will help to keep your tank crystal clear. High water quality keeps your fish healthy and ‘hoovering’ your substrate can aid in keeping the numbers of the ‘Ich’ parasite extra low.

Mature filtration is also essential. As I mentioned at the start of this article, your filter actually kills Ich, as bacteria in the filter trap and eat the parasite, so adequate filtration is always necessary and will help if you have a case of white spot to deal with.



Final thoughts

Always remember that prevention is better than the cure.

But If you are unfortunate enough to have an outbreak of White spot/Ich in your aquarium then keeping the tank clean and having proper filtration is key in defeating it.

There are loads of medicines available to help too.

Quarantine new fish if you can.

If you do get hit with an outbreak of White spot, remember to remove any activated carbon from your filter, or anything else that will absorb any medication. Follow the instructions carefully and always treat over an extended period (usually 7 days for most meds) to prevent the problem from reoccurring.

Don’t remove any other media from the filter though. Your filtration is the key to your fishes survival.


Here’s a link to some effective medication if you’re in need: Link


Effect of high water temperature (33 C) on the clinical and virological outcome of experimental infections with white spot syndrome virus

ICH (White spot disease)

Fish parasites

Vetinary parasitology

About the author

James @Seriously Fishy

I am a fish keeping enthusiast with over 20 years experience. I currently keep American Cichlids (CA) which are my favourite fish to keep so far. I started Seriously Fishy as I noticed a large volume of people on various web pages looking for help with Aquarium basics. I created the first Seriously Fishy book to solve the issue in 28 pages, that led to the Seriously Fishy UK fish forum and blog.

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