There are few diseases more hated and feared in the aquarium hobby than Ichthyophthirius multifiliis. Of course, most people just know it as freshwater ich, or white spot disease, but nearly everyone has battled this freshwater parasite at one time or another.
And it is by far one of the most common fish diseases out there, and sometimes the most persistent. I can’t even count the number of times I thought I had eradicated it from an infected aquarium, only to watch as it came roaring back. And then I had to watch helplessly as it wiped out fish already weakened from the first round of the parasite.
But there are ways to treat it, and most importantly, there are ways to prevent it from ever entering your fish tanks. In this article, you’ll learn how to identify freshwater ich, and what the best treatment options are for any infected fish you may have.
What is Freshwater Ich?
Ich is an ectoparasite, and what that means is that it’s a parasite that lives outside of its host. Other common ectoparasites are ticks and fleas, and like these parasites, ich attaches to its host and feeds on it.
These parasites are commonly found on wild freshwater fish, but for some reason they are far more prevalent in aquariums. It could be due to the cramped conditions in aquariums, or it may have something to do with the increased levels of stress in captive fish. But whatever the reason, freshwater ich is far deadlier in a fish tank than in the wild.
How to Identify Freshwater Ich
It can be difficult to spot a fish infected with ich – especially in the early stages of the infection. But if you look closely, you will see an infected fish will have numerous little white nodules on its body, that almost resemble tiny grains of salt. Each of these white spots is an encysted parasite, preparing to reproduce.
If you’re observant, you may notice ich when it’s isolated to only a few fish. But more often than not, it’s usually only discovered after its spread to most of the fish in aquarium. And by this point, the fish will often be infested with parasites, and the situation will be critical for them.
Infected fish will also display other symptoms, and you should also keep an eye out for any of the following symptoms:
- Loss of appetite and weight loss
- Rapid breathing
- Swimming upside down near the surface
- Flashing, or scratching up against decorations or the substrate
- Hiding and not schooling with other fish
However, this behavior doesn’t occur in newly affected fish, so it’s important for an aquarist to keep an eye on their fish so any ich outbreak can be treated as quickly as possible. Early treatment is essential if there is any hope of the fish returning to normal health.
Life Stages of Freshwater Ich
The ich protozoan goes through several life stages. In the first stage, the ich trophont burrows under the fish’s mucus coating, and forms a nodule. During this stage, the ich parasite will feed off of the fish for several days until the nodule is fully developed. The ich parasite is immune to any chemical treatments during this stage.
After the trophont has fed off of the fish, it will detach and become a tomont. It will often float in the water for several hours, until it becomes attached to a hard surface. After it has become attached, the parasite begins to rapidly divide, creating hundreds of daughter parasites, also known as tomites. They can replicate in as little as 12 hours, though generally they take longer.
The tomites will then hatch and become theronts, and they will begin to swim around the aquarium looking for a new host. They have only a short window to find a host, and they will die after 48 hours if no host is found. Once they’ve found a host, they will become trophonts, beginning the whole cycle over again.
This cycle can take anywhere from 7 days to 8 weeks and the speed of the cycle is greatly affected by the water temperature. The cycle moves very slowly at low temperatures (taking upwards of 8 weeks at 39oF or 4oC), and moves much more rapidly at higher temperatures.
How Dangerous is Freshwater Ich?
Make no mistake about it – ich is a deadly parasite. If left untreated, it has a 100% mortality rate, and it often leaves fish weakened, or permanently disabled, even after it’s been treated.
It can cause considerable damage when it’s located on the gills, as the parasite reduces the fish’s respiratory efficiency. This can lead to the fish having difficulty breathing, and if the aquarium has low levels of dissolved oxygen, the fish can even suffocate.
Infected fish will slowly weaken as the number of parasites feeding on them increases, and the lesions left in its skin can often lead to secondary fungal or bacterial infections.
It’s important to realize that this parasite can kill your fish, and the faster that the treatment commences, the better the chance your fish have of making a full recovery.
What Increases the Chance of a Freshwater Ich Outbreak?
While recent research seems to contradict the view that ich is present in all aquariums, it is still likely present in many fish tanks – especially since some fish can be carriers with few detrimental side effects. And even a single ich parasite can quickly cause a major outbreak.
So, it’s probably best for the average aquarist to assume ich is lurking somewhere in their aquariums, and to take steps to avoid triggering an outbreak. While no single factor will cause an ich outbreak, there are several ways to try and avoid it.
One of the best ways to keep ich at bay is to limit the stress fish are subjected to. Fish with high levels of stress are far more susceptible to ich, and they will have a much higher mortality rate. But a healthy, happy fish is generally more resistant to illnesses, and this is especially true with freshwater ich.
Low levels of stress can be achieved through not overstocking an aquarium, and by ensuring all of the fish species are compatible. When this is combined with a high quality and varied diet, a fish will usually have very low levels of stress – and be far more resistant to ich.
Another way to prevent ich outbreaks is to keep the water as close to pristine conditions as possible. Almost nothing is worse for a fish than poor water quality, and while ammonia, nitrites and high levels of nitrates in the water won’t cause outbreaks on their own, they will speed them along.
Freshwater Ich Treatment
Ich is probably as old as the hobby itself, and numerous treatments have been developed over the years for this parasite. But before you start any treatment, you need to know that what works for one fish, might not work for another.
Probably the best way to treat an ich outbreak is by simply raising the temperature. Ich can’t replicate at temperatures higher than 86oF (30oC), and while most fish are unable to handle these temperatures for long, it can be a good, non-toxic way of treating an ich outbreak.
And even if you can’t raise the temperature that high, raising it even a few degrees speeds up the parasite’s life cycle, and allows the chemical treatment to target ich in the tomite phase – one of the only times where it is susceptible to medication.
However, this treatment should only be used for a few days, and it’s usually safer to only increase the temperature to the 76-80oF (24-27oC) range. Anything more, and it might be too much for already sick and weakened fish to handle. Also, this should not be done for cold water fish, as it may cause oxygen starvation.
It’s also a good idea to increase oxygenation of the aquarium during heat treatment, and this can be done through the addition of an air stone, or by increasing the flow of a hang-on-back filter, as this creates more surface disturbance, which in turn aerates the water.
Another treatment option often used in conjunction with heat treatment, is to use one of the commercially available medications. The two most commonly used ones are formalin and malachite green, though I personally prefer Seachem ParaGuard, which is blend of malachite green and other substances. It also tends to be far less toxic and easier to use than formalin.
There are several other medications available, including copper and methylene blue, but these have been shown to be no more effective than formalin or malachite green, and they tend to be more difficult to find.
Prior to treatment, any carbon inserts in filters should be removed. These can be replaced when the treatment has been completed, but if they are left in during treatment, they will remove the medication from the water.
It’s also important to do several water changes when you have completed the treatment. The chemicals need to be removed from the water, and you don’t want to expose your fish to them any longer than is necessary.
Also, before using malachite green, it’s important to note that it may stain silicone and decorations green. It can also be toxic to certain fish, and if you are treating scaleless fish (i.e. catfish), or native North American fish, it should only be used at half strength.
Another less commonly used treatment is leaving chlorine in the water, as it has the side effect of virtually wiping out beneficial bacteria (the bacteria that process ammonia and nitrites). While the other methods will damage filter bacteria, it is believed they don’t do as much damage as chlorine.
But if you can deal with a potential spike of ammonia and nitrites, and are able to do daily water changes, chlorine can be a very effective treatment for ich. Most of the ich parasites will disappear after a few days, and the rest will be gone after a few weeks.
However, this is mainly done in large ponds or very large aquariums, where the other treatments aren’t feasible. Also, the huge volume of water in these larger environments means that spikes in ammonia or nitrites likely won’t be as toxic – something that can’t be said about small home aquariums.
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Ich is far less tolerant of salt than freshwater fish, and by raising the salt concentration in an aquarium, it can be an effective way to treat ich. This is often done in conjunction with heat treatment, and along with the sped up life-cycle, it can often remove ich in a matter of days. It also has the added benefit of helping fish to develop their slime coats, which protects them from parasites.
If you can manage to get a concentration of 1.002 g/cm3, it should wipe out the ich parasites. This usually translates to about one (1) teaspoon per gallon (3.8 liters) in aquarium. Only aquarium salt should ever be used, and it’s important to avoid table salt with added iodine. If you’re having trouble finding aquarium salt, you can always find affordable Aquarium Salt at Amazon.
Also, while salt treatment is effective with heat treatment, it should never be used with any medication. Salt and medication may react together in the water, which can restrict oxygen. This can be incredibly deadly to fish likely already suffering from respiratory problems, in a tank with lowered oxygen levels from the increased temperature.
Fish Removal Treatment
Due to its reproductive cycle, ich are dependent on the fish staying in the aquarium. If the fish are removed from the fish tank, then the tomites have no fish to latch onto and will quickly die off.
Obviously, not everyone will be able to do this treatment, as it can be difficult to have another cycled aquarium ready for sick fish. Also, the fish removed from the aquarium still need to be treated for ich, or there will be a fresh outbreak in their new tank.
But this can be effective when used properly, and can be an excellent way to deal with a major ich outbreak. And at the very least, it will greatly reduce the number of parasites that need to be dealt with.
Final Word on Treatments
Regardless of which treatment you choose, the fish will likely be stressed and weakened by the end of it. It’s very important to do several water changes (if only to remove any left-over salt or chemicals), and to keep a close eye on the water parameters for several weeks.
Preventing Freshwater Ich
While much of this article has been dedicating to identifying and treating ich, one of the most important ways to battle this parasite, is to make sure it never makes its way into your aquarium in the first place.
Quarantine New Fish and Plants
It usually takes a few hard lessons before new aquarists setup a quarantine tank. But after you introduce a new fish or plant to your home aquarium, and watch as a disease ravages the fish you’ve raised from fry, it’s usually not long before you setup a tank for quarantining new fish.
Not only are disease treatments easier to do in smaller quarantine tanks, but it stops the spread of illness before it can reach your main tank. And while it can be unfortunate to lose new fish to an outbreak, it’s better than the alternative of a massive die-off.
New fish should be quarantined for a minimum of three weeks, and at the end of this time, any of the more common diseases or parasites should be easily visible.
Never Add Fish Store Water to a Home Aquarium
The fact that you should never, ever add fish store water to your aquarium is not very well-known among new aquarists. While the fish you are adding to your aquarium may be healthy, store tank water can often host numerous diseases and parasites – including ich.
When you bring home a fish in a bag of water, the fish should be netted out of the bag, and the water should be discarded. The fish should then be added to the aquarium – without the net dripping on or touching the surface of the water.
Only Purchase Healthy Fish
Before you buy a fish, always carefully scrutinize the tank you’re purchasing from. Are all of the fish healthy? Are there any signs at all of white spot disease? If you even suspect that there might be ich in the local fish store’s tank, don’t buy any fish from it.
Even if the fish you choose appear to be healthy, but there are other fish showing symptoms of ich in their tank, it will still have been exposed. And it will almost certainly carry the ich parasite back to your home aquarium. Some fish are able to act as carriers without showing any overt symptoms, and can quickly cause an outbreak when introduced to a new tank.
Don’t Share Nets or Plants Between Tanks
One of the most common ways to spread parasites like ich between aquariums is by sharing aquarium equipment. Plants, nets, and decorations can all infect other fish tanks if they are moved between aquariums without completely drying out first.
This is especially true during an ich outbreak, and anything used on the infected aquarium shouldn’t be used on any other fish tanks. Period. It is imperative that it isn’t given a chance to spread.
While freshwater ich is a deadly and resilient parasite, if you follow the information in this article, you will be well prepared to deal with it. And the good news is that fish who survive an ich outbreak often become more resistant to it. So, if they make it through one outbreak, it’s unlikely they’ll be affected again in the near future.