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Fish Tank Guides / Illness and Disease

White spot/Ich – Fish illness

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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 chances are, that this parasite is already in your aquarium, even if they haven’t affected your fish yet. This is a parasite that can always exist in small numbers in your aquarium, waiting for a chance. The immune system of your fish keeps it in check, by not allowing it to infect them the numbers of the parasite remain low as it is unable to feed and reproduce. If a fish’ immune system becomes weakened, through stress or other illness, this gives the White spot/Ich parasite a chance to strike.

White spot can reproduce quickly and is very capable of wiping out an entire tank. It has a high mortality rate and is an extremely common disease to see in the home aquarium.

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.

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. Where 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.



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 raised white dots and can sometimes appear to look like grains of sand 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 until 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 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 treatment 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 though, many treatments will only affect the parasite whilst it is at certain stages of its lifecycle.

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

Any infected fish should ideally be moved to a separate quarantine tank. The White spot / Ich parasites will soon break free of that fish and will then reproduce. Removing the fish from your main aquarium means that the reproduction won’t take place there, thus preventing your other fish from being infected, hopefully.


There are a couple of ways to stop the spread of Ich that do not involve chemicals. This was often recommended as an additional treatment on top of chemical treatment and it can help.

The White spot parasite life cycle is quite short, increasing the temperature in your aquarium shortens it still. This means that, if your fish can tolerate it, raising your temperature to 30 degrees Celcius shortens the lifecycle of the parasite. This means that you are more likely to catch it at the stage of its life cycle where the medication will be effective.

Secondly, most parasites cannot tolerate salt, so adding aquarium salt to your tank will help to kill it.


You may have noticed that I said this ‘was’ often recommended. That is because many now see this method of treatment as outdated, with some reports claiming that it is ineffective.

The Ich parasite can make it difficult for your fish to breath. Increasing water temperature and adding salt only make 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.

Salt in the water has the same effect. So when you combine all three, there is a risk that rather than Ich killing your fish, they will suffocate.

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

White Spot Medication



Prevention of White spot/Ich

White spot or Ich is in almost every aquarium, it occurs naturally, so how do we prevent it?

As i mentioned, this parasite only affects your fish initially if they have a reduced immune system due to stress, or other illness. Once it has infected one fish it then reproduces, creating thousands more, which will then begin an onslaught on all the other fish in the tank. This will reduce their immune system function and in turn mean they are then infected, and the cycle continues. Nightmare.

So, a good way to keep your fish healthy is to keep them stress free. This is good practice anyway, keeping them in the correct environment, with places to hide and keeping up a good maintenance routine will ensure that your fish stay stress free and healthy.

Having a quarantine tank is a great idea, not only is it handy if one of your fish becomes ill, its 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 riddled with little white spots within a few days.

Adding a sick fish to your aquarium can spell disaster, so if you quarantine it for a week or two in its own tank first, you can be sure that it is healthy and disease free before adding it to your main aquarium, keeping your existing fish safe.

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.



Final thoughts

Always remember that prevention is better than the cure. If you are unfortunate enough to have an outbreak of White spot/Ich in your aquarium then you need to act fast to prevent it spreading. It is always ideal to have a quarantine tank on standby, just incase, and always quarantine new fish.

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 the medication. Follow the instructions carefully and always treat over an extended period (usually 7 days for most meds) to prevent the problem from reoccurring.

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

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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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