Disease – Signs, Causes, And Cures

Tropical Fish, Aquarium, Fish, Fish Tank

It is a fine lazy day and you are just kicking back and enjoying the aquarium you have worked so hard to set up. One of your fish looks like he has been rolling in the sand. And yet another seems to have less fins than you recall. And still another is bloated he looks as though he’s going to burst. In general, it looks as if your fish are sick! Yup, keep fish long enough and it is something that you’ll have to face eventually, and usually fairly early unfortunately. You see, illness is often preventable, but typically we only learn how to do this after doing it wrong the first time. Many disorders can be turned around if spotted early and treated correctly.

Spotting Illness

So how do you tell that a fish is sick in the first place? It’s not like they’re going to tap you on the shoulder and allow you to know. For the most part the only way you’ll know something is wrong is through careful observation of their appearance and behavior. Hopefully you’re already pretty well acquainted with what could be considered normal for your fish and can thus notice when something is off. Here are some key things to take note of:

-paleness/color change

-clamped fins (the fins are held close to the body)

-scraping or rubbing against objects in the tank

-heavy breathing

-loss of appetite


-decreased activity

… and of course the more obvious signs like visible sores, swelling, and such.

Keeping a watchful eye out for signs of illness is an important part of keeping fish. Try to take a few minutes each day to check for any signs that something is amiss. An illness caught early is far easier to treat and the odds of the affected fish surviving the ordeal are much greater. For many ailments your fish may face by the time it’s blatantly obvious it is too late.

Quarantine Tanks

Obviously one step better than treating your fish once they become sick is preventing it from occurring in the first location. The absolute best way to prevent diseases from reaching your tank is using a quarantine tank. A quarantine tank is essentially only a small bare bones aquarium setup where new arrivals can spend a week or two before entering your main installation. This gives you ample time to make sure your new fish are in good health before they have an opportunity to possibly spread any Opossum Poop to your other fish. It also gives new arrivals a opportunity to get over the stress of going in a quiet and serene atmosphere. And if a problem does arise with the shredder already isolated makes treatment much easier as well. Finally, in case a problem does reach the fish in the main aquarium the quarantine tank can serve as a hospital tank also, preventing the further spread of illness and providing a safer and more controlled environment for the application of any treatments.

Besides a quarantine tank, maintaining your fish in good general health goes a long way towards preventing any illness from taking hold. Most common ailments often arise in fish only if their health is already compromised. What causes their health to become compromised? The majority of the time the culprit is poor water quality. A fish trying to reside in filthy water in kind of like you trying to live in a home full of smoke- it is unlikely you’re going to be in the best of health. Keeping on top of your aquarium installation’s maintenance is crucial to keeping your fish healthy and disease free. As such, if your fish ever become sick your first step should be to make sure the water is in great condition. All the critical parameters, such as ammonia, nitrate, pH, and temperature, should be assessed. Always be suspicious of any equipment or decoration that has been recently added to the tank as well which might be leeching something toxic into the water. Andif poor water quality isn’t the root cause of this illness, a water change is never a bad idea once it comes to retrieval the cleaner the water the better.

About Medications

Often people go straight for the drugs at the first sign of an illness in their fish, usually without even knowing what exactly is wrong. This isn’t a good move. Positive identification of a disease is absolutely essential before beginning application of any medication. Many medications aren’t exactly easy on your fish either meaning using the wrong one could end up further stressing your fish without curing their illness, probably leading to death. Still, in case you encounter a disorder where a medication is applicable it can be a true life saver. Just make sure you remove any carbon from the filter prior to beginning treatment as it will soak up the medication until it has a chance to act. And, it should go without saying that the directions should be followed to a T. Pay special attention to any warnings dealing with species the medication shouldn’t be used with. Some, for example, will kills snails and plants if there are any from the tank.

Common Ailments

There are tons and tons of ailments your fish may face- much more than what are listed here. However, many are fairly rare, affecting just a few specific species or just arising under specific conditions. Instead, this list tries to cover only the most common ones that most aquarists have a tendency to run into.

Ammonia Poisoning/New Tank Syndrome

Signals – red irritated gills, fish gasping for air at the surface, most common in fresh tanks

As the common name of’new tank syndrome’ suggests, this is typically only a problem in freshly setup aquariums, though it can occur is older systems when the filtration system is severely damaged. Basically, not all bacteria are out to make a meal of your fish. Some are actually quite helpful, and necessary, to your aquarium. Their job is to process the fish’s waste from highly toxic substances, namely ammonia, into compounds they can more easily withstand. The process of establishing these germs in a new system is called cycling. Unfortunately, this measure is often skipped resulting in a buildup of ammonia that in short order leads to dead fish.

Remedy: water changes

To solve this issue you basically just need to keep the water clean through regular water changes before the bacteria have established themselves and may take over. A test kit for ammonia is very helpful here as ideally you want to keep the ammonia level under 1ppm. Typically you’ll need to do a small water change daily for a couple of weeks to allow the cycle to complete while keeping the tank habitable for your fish. Keeping feedings light during this time can also help keep the waste load low which in turn keeps the water cleaner.

Fish Fungus

Signs- fish has fuzzy whitish globs or stains attached to its fins or body

Like a lot a ailments you’re going to experience, fish fungus usually appears on fish whose health is already compromised. This normally wouldn’t be a issue, but if a fish is already in poor shape the fungus can find a hold very easily. It often starts at the site of an accident, which could be anything from minor scrapes to significant sores, and spreads quickly from there.

Treatment: medication for fungal infections

The best way to treat fungal infections is with medication designed for them. Of course making sure the tank is in good shape is key and the fish is likely already in poor shape and needs all the help he can get recovering. As a side note, many remedies for fungal infections also work against bacterial infections which could bring some added advantage if the fish’s initial poor health was caused by one.

Signs- fish is coated in lightly colored specks or has a dusty look


Ask people to name a common fish disease and ick is probably the one you’ll get. It appears just about everyone who’s ever kept fish has had to deal with it at some point or another. What’s more, it’s quite easy to spot compared to other diseases and so seems to stick with people. When you haven’t encountered it before, ick is a parasite that burrows into the fish’s skin causing small white spots that make it appear as though your fish has been salted. Outbreaks often occur after the addition of fresh fish, which bring ick along with them, although it can also limp along in a tank for a very long time until conditions are favorable for a explosion. Like pretty much every disorder, favorable conditions means fish in poor health with the most frequent reason being poor water quality.


Velvet is less common but still worth mentioning. It’s another parasite that acts much like ick, appearing as stains on the skin.

Remedy: medication for parasites

They are both parasites with a similar life cycle- part of that is spent attached to a fish and part of which will be spent free swimming. Killing them is more or less impossible while they are safely burrowed beneath the fish’s skin. It is only when they emerge into the open water to search for a new host that they are vulnerable. This means treatment can take some time. Medication needs to be implemented for an elongated period to wait out the parasite’s natural life cycle, which can take up to a month. Raising the temperature of the aquarium a few degrees can help speed things up a bit. Also one other note- these parasites do need a fish host to complete their life cycle. So, should you move all of your fish into quarantine for therapy, any parasites left at the primary tank will die off after about a month.


Signals – fish is bloated, and possibly with the scales giving it a pine cone appearance

Dropsy is not a disease itself but rather the physical outcome of some other ailment, usually a bacterial infection although it could be brought on by any number of other things. The swelling is brought on by a buildup of fluid in the fish’s body cavity.

Treatment: medicine for bacterial diseases, aquarium salt

Unfortunately by the time the symptoms are clearly visible it’s often too late to save the fish. Still, the best course of action is to move the fish to quarantine and start administering an antibiotic, preferably in the shape of an medicated food. Adding a small amount of aquarium salt may also help the fish expel some of the excess fluid thus alleviating the swelling. Use around one tablespoon per five gallons.

Swim Bladder

Signs- fish has difficulty maintaining equilibrium and may have trouble controlling depth

A fish’s swim bladder is sort of like a ballast tank in a submarine, only with air rather than water. They use it to keep themselves upright and in the correct depth. If it becomes damaged or otherwise perturbed the fish is no longer able to control this air and so will usually either sink to the bottom or float to the top, often in an off-kilter orientation.

Treatment: fasting/cooked peas, medicine for bacterial infections

Unfortunately there’s not a lot of consensus on the exact cause (and in fact there are at least a few possible causes) or how to deal with it. Making sure the tank’s chemistry is in good shape should be your first step of course, as it should be with any problem. One frequent cause is a blockage in the fish’s digestive system. The typical solution for this is shelled cooked peas (they are sorta the go-to fish laxative). Backing off feedings for a few days can also help. If not then it might be the symptom of a bigger disease in which case a medication can be attempted. Unfortunately it can also sometimes arise because of trauma sustained during transportation in which case there is not much that could be accomplished. In these situations all you can do is give the fish a place to recover and hope for the best.

Pop Eye

Signals – fish includes a protruding eye

A pretty self explanatory title, the fish’s eye or eyes bulge out of the fish’s head as if they’re on the brink of falling out completely. Once again this isn’t so much linked to any one specific cause but instead might originate from a couple possible resources, namely injury or an illness.

Injury due to fighting or from bumping into something is probably the most common. Think of it like the fish equivalent of a black eye. In this case the best you can do is prevent any fighting and supply your fish with a calm home in which to recover.

Another possibility is a bacterial infection. If both eyes are popped then this is much more likely, although the fish should still be checked for signs of injury or fighting. A good medication is the best course of action here.

Add one tablespoon per five gallons and watch to see if it has any impact. Bear in mind this can help alleviate the swelling but won’t resolve the underlying problem and as always your first step should be to make sure the water is in great shape.

Signs- fish has a cloudy eye

The creatures of the world have all kinds of interesting eye with assorted colors and shapes and whatnot. One thing they all have in common, though, is that the center is clear and nice. Should you ever notice your fish’s eye or eyes becoming milky then something isn’t quite perfect.

There are a handful motives a fish’s eye may become cloudy. Parasites or germs are possible causes, particularly if the eye has been hurt. Poor diet or even cataracts as a result of old age are potential culprits also. However, the most likely cause falls based on so many other issues – poor water quality. Getting the tank is fantastic shape should be your first concern if your fish develops muddy eyes. Pay particular attention to the pH as a particularly low pH is considered to contribute to this problem. Check that you are feeding your fish an appropriate diet also. With better water quality and a proper diet the problem should clear in a couple weeks. However, if the problem does not clear after several weeks with improved conditions an antibiotic can be attempted.

Hole at the Head/Lateral Line Disease

Signals – fish has holes in its head

The name is fairly self explanatory, and the indicators are easy to spot, so all that leaves is the cause. Why are there undesirable holes in your fish’s head? Unfortunately there’s no consensus on the precise cause. It may be brought about by some specific pathogen, but none has been positively identified as of yet. Some think overuse of activated carbon or nutrient deficiencies might have something to do with it as well.

Treatment: improve conditions, diet modification

Ultimately, the best course of action is to improve conditions as much as you can for your fish. Measure up the water changes and try removing any activated carbon from your filtration. Try to include as much variety to your fish’s diet as you can. Frozen in addition to vitamin enriched flake foods are fantastic sources of vital nutrients your fish may be lacking.

Fin Rot

Signs- the fish’s fins are deteriorating

Fin rot is another disorder that isn’t so much about a specific contagion as opposed to a result of the fish’s overall health. Fin rot typically only affects fish which are already stressed or weak because of something else like poor water quality, malnutrition, bullying, or possibly some other illness, at which point bacteria move in and begin feasting on your bad fish’s fins.

treatment: improve conditions, medication for bacterial infections

Your first course of action should be to determine why the fish’s health has slipped in the first place and correct it. Check the water quality and change to high quality vitamin supplements if you haven’t already.

Again, the majority of the time health problems come down to a water quality problem. Keeping on top of your aquarium maintenance program is the best way to prevent problems in the first location. Likewise, if an illness should attack assessing the water parameters should be your first step. Many problems will clear by themselves with improved conditions. And when a medication becomes necessary make certain to follow the directions extremely closely. An overdose of medicine can be just as bad if not worse than the disease itself.

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