Fish Disease

Fish disease is another common aquarium problem that most aquarists will have to address at some point.  Fortunately, there are precautions one can take to minimize the adverse effects of fish disease in the aquarium.

Fish Diseases and Fish Compatibility

The first thing one should keep in mind is that fish disease mostly will affect weakened or stressed fish.  This is why being mindful of Fish Compatibility is so very important.  If you place a passive fish with a tank full of more aggressive fish then it is highly likely to become susceptible to disease if it is not outright killed.  The more aggressive fish will harass and badger the more passive fish and create great stress on it, greatly increasing the likelihood of it developing a disease.  Unfortunately, even when care is taken, fish that would normally be compatible can become victims of bullying by other fish in the tank.  If this becomes the case, then the merciful removal of the victimized fish before it infects others in the tank can be the best scenario.  However, if there is one fish that is doing the bullying then the removal of the most aggressive fish can restore balance to the tank.  When establishing an aquarium system this sort of scenario will inevitably play out before you develop a balanced community of fish in the aquarium.  With many species of fish, multiple females per male will make the males much happier and less aggressive.  Having multiple males per female will likely result in an overly aggressive tank susceptible to disease outbreaks among multiple fish.  Keep in mind that treating the individual fish and disease itself will be unlikely to be successful without a balance in the tank.  There are instances where the entire tank can become diseased as a result of an imbalance of the aggressiveness or an entire group of fish will become sick and die.  The role of fish aggressiveness and compatibility on fish disease can not be understated.

Fish Disease – Buying and Acclimating New Fish

There are a lot of other factors in fish disease however.  When you buy fish online or in a fish store, they have already taken a long trip to get there and this can create stress on the fish and make them more susceptible to fish disease.  Before you introduce any new fish to the aquarium look carefully for any signs of fish disease.  It is best to have a quarantine / hospital tank.  A 10-20 gallon tank with a small hang on back or internal filter will make a good quarantine / hospital tank for many systems.  (AD) Any new fish can kept in the quarantine tank for the first few days to make sure no disease appears.  Even with a quarantine tank, disease can appear after being placed in the main tank due to stress caused by the other fish or improper acclimation.  Acclimation when introducing any fish to a new system is imperative.  To acclimate a fish one should place the bag with the new fish for 15 minutes to let the temperature adjust and let the existing fish become aware of the new tank mate.  Then punch or cut a small hole in the bag to let some of the water mix between the water in the bag and the tank.  If you do not want the water in the bag to get into the tank (due to possible contamination) then slowly add water from the tank to the bag and discard an equal amount of water from the bag.  The purpose of this is slowly bring the pH and water chemistry of the bag to the same levels as in the tank.  The total process should take between 30-45 minutes.  You need to make sure the bag has enough oxygen during this process.  Acclimation systems are available to assist with this process. (AD)  Adding water conditioner when introducing a new fish to a new environment will also help reduce the chance of disease developing.

Types of Fish Disease- Ich

By far the most common type of fish disease encountered is parasitic and is called Ich or Ick.  Ich is a protozoan disease that is often called ‘white spot disease.  It is caused by a microscopic protozoan parasite called ichthyophthiriasis in freshwater but a similar parasite called Cryptocaryon in saltwater causes saltwater Ich.  It can occur in both freshwater and saltwater species although it is due to different species parasites.  The symptoms are the same in freshwater and saltwater fish and treatment is similar. (PICTURES)

The symptoms of ich are very evident and usually include characteristic white spots on the body and gills. In some infections, the ich organisms will only be found on the gills. As the disease progresses, the fish will become more irritated and may try to rub or scratch against the sides and bottom of the tank. The disease may then cause respiratory distress, severe agitation, loss of appetite, and eventually death.

Ich can spread to and infect an entire tank.  However, a healthy and well adjusted fish in a tank that otherwise has good water quality will usually have a fair amount of tolerance and ability to resist infections.  If you see an infected fish and remove it to a quarantine tank right away then chances are good that the infection will not take hold in the entire tank.  This is preferable as treating an entire tank will take 2-3 weeks and can disrupt the water chemistry in other ways.  It will require a lot of work and water changes to restore the tank back to normal.  If you can remove an infected fish within the first 24-48 hours then chances are that this can be avoided.  If you remove a fish then you will either need to eliminate it or quarantine the fish to a quarantine tank.  Once the infected fish is removed then we recommend the continuous use of a UV sterilizer, large water changes, and frequent addition of water conditioner for two weeks as a precaution.  Afterwards, if no further sign of infection is apparent then beneficial microfauna can be reintroduced to the tank.

Treatment includes formalin, malachite green, copper, or a combination of these. Methylene blue, and baths of potassium permanganate, quinine hydrochloride, and sodium chloride can also be used.  When using formalin, make sure to use recently purchased formalin. Formalin that is stored for long periods of time can convert to paraformaldehyde, which can be toxic to fish. An indicator that this has occurred is the formation of a white precipitate in the bottle. Malachite green may also stain some decorations and silicone to a green color and may be toxic to piranhas, neons, sunfish, and some scaleless fish.  Use according as directed.  Lower temperatures and making the salinity different from the main tank can also help kill the parasite.  However, the fish will have to be carefully acclimated to prevent even further stress on the fish.  A quarantine tank with a combination of anti-ich medications and treatments will offer the best chance for a successful cure.  Even so, the fish is likely to succumb and only if the fish is completely cured and no symptoms are apparent for at least a week should re-introduction back to the tank be attempted.

If the infection spreads in the tank then the entire tank might need to be treated.  Some of these medications will kill invertebrates and beneficial microorganisms and bacteria in biological filters.  Some will also permanently stain some of the tubing in the system.  You will have to remove a denitrator filter from the system and let it circulate in a separate tank or bucket while this is done.  After 2-3 weeks you will need to use carbon and do water changes to remove the medication from the tank and gradually bring the system back to normal.  This can be time consuming and there is no guarantee that you will save most of the fish.  By far, the best way to deal with this is to not add any infected fish in the first place and if a fish becomes infected to remove it from the tank immediately before other fish become infected.

Types of Fish Disease- Other Diseases

There are countless other diseases that fish can get even though Ich is by far the most common.  Fish ailments can be separated into 4 general types including bacterial infections, fungal infections, parasitic or protozoan infections, and physical ailments and wounds.

The cost and trouble of treating a fish versus saying a little fish funeral prayer and flushing it is up to the aquarist.  If it’s a valuable fish that you are attached to then treatment makes sense.  If it’s a common and relatively inexpensive fish that you just got then frankly it might be better to move on.  If you have had it for years then you might be attached to it, but the disease is very likely due to old age and treatment will be unlikely to be successful.

Bacterial Diseases: Bacterial diseases are usually characterized by red streaks or spots and/or swelling of the abdomen or eye. These are best treated by antibiotics such as penicillin, amoxicillin, or erythromycin.

Fungal Diseases: Common fungal infections often look like gray or white fluffy patches.  The fish may have erratic swimming, darting, scratching, or visible cotton-like tufts on skin, eyes, or mouth.  Anti-fungal medications are available that can even be safe to treat the entire tank with although a quarantine / hospital tank is nearly always preferable.

It can be difficult to pinpoint whether a disease is bacterial or fungal in nature and multiple sources of disease can be present.  If this is the case a quarantine / hospital tank with multiple medications can be the best bet to successfully treat a fish.

Parasitic Diseases: There are a few other parasitic diseases other than Ich that fish can get.  Their treatment is the same as that for Ich.  They will often look slightly different from Ich in that instead of white spots, small wormlike flukes or flea looking creatures will be attached to the fish.

Physical Ailments: Physical Ailments are often the result of the environment. Poor quality water conditions can lead to fish gasping, not eating, jumping out of the tank, and more. Tank mate problems can result in nipped fins and bite wounds.  Quarantine might help heal the fish but if it’s put back in the tank with an aggressive fish that caused the problems then it will just happen all over again.

Fish Disease: Water Quality and Diet

Many fish require higher water quality than others.  Some, such as freshwater Cichlids or saltwater Damsels, typically thrive in both aggressive environments and can tolerate relatively poor water quality.  Others such as freshwater Discus or Saltwater Butterfly fish require much higher water quality or will not do well in aggressive environments.  Other fish, notably saltwater Tangs, but also many species of other saltwater and freshwater fish will become diseased if they are not given a proper diet.  Tangs definitely require algae sheets to feed on regularly and many other fish will suffer and become ill if they do not receive a proper and varied diet.  This is why it is so important to do your research and due diligence when you purchase any fish.