Many aquarists especially the beginners are left confused when their newly brought fish die the next day or in a week. Sometimes, Aquarists also notice that some other fish die after introducing a new fish to an Aquarium. Unknowingly, an aquarist has brought home a diseased fish from a local fish store. Knowing how to prevent death, and control disease to a manageable level will ensure the enjoyment of the hobby and not lead to undue stress. After all, an aquarium needs to be the center of conversation in every home. So how do we know the common disease in an aquarium? how to control and prevent an outbreak of disease? Let us read on and find out.

Why do fish get the disease?


How many times did we go beserk on purchasing every kind of colorful fish in an aquarium? It is easy to be overwhelmed by all the fish available at the local fish store. Too, many fish in an Aquarium will deplete the level of oxygen in the tank. Every species have a different level of water parameter requirement. Simply, overcrowding the tank will also result in competition for the establishment of the territory thereby resulting in chasing and injuring the fish. Overstocking also results in Ammonia, Nitrite issues which is the main cause of fish death in a closed environment. Overcrowding in an aquarium is a major cause of fish disease.


Fish are classic actors and always behave as if they are hungry. The most cardinal mistake done by an aquarist is to overfeed the fish in an Aquarium. In wild, most of the fish do not get their feed for days but yet they survive and we tend to overfeed in an Aquarium sometimes 3-4 times a day. It is an instinct by children or even by the elderly who are told to care for the fish to tend to overfeed the fish left in their care. The fish will always approach the front end of the glass begging for food. The uneaten food can result in pollution of water thereby causing fish disease. 

Water Temperature

The body temperature of the fish varies with the water temperature. The weather patterns or even the presence of an AC in the room will alter the temperature of the water. The resistance of the fish to adapt to these sudden changes takes time. Some of the delicate fish like the Tetra cannot adjust and they die.

Non-Sterilized Equipment

This is an unforeseen mistake by an Aquarist. Nets that are used in an Aquarium or any tool should be sterilized. Many a time an aquarist uses the same tools across many tanks. Tools carry germs and parasites, unknowingly transfer to other tanks.

Getting home an infected Fish

It’s always good to get your fish from a well-maintained LFS (Local Fish Shop). Never buy fish from a shop when it has just arrived. The fish in an aquarium shop is kept in a very crowded environment. There is a potential risk of disease by carrying an infected fish at home and not Quarantining it appropriately. The newly infected fish can pass off its disease to other healthy fish already in the aquarium.

Now let us look at some common diseases that occur in an Aquarium. 

The disease needs to be controlled and manageable. Any lapse in taking precautions can result in an outbreak of the disease in a tank.

Ich/White spots

This is the most common disease faced by an Aquarist sometime or another. This happens due to changes in the water temperature. You will see white spots on the gills, bodies, and fins of the fish. It looks like sprinkled salt. This is the most visibly seen disease on a fish.

In the beginning, the infected fish will rub its body across hard objects causing injury. The fish in this case tends to lose appetite and stay in a corner. If not treated the fish can die. This disease is highly contagious.

This disease can be treated by raising the temperature by using an effective heater and medicine. 

We use seachem paraguard for effective treatment of the fish and the aquarium. An aquarist needs to treat the entire tank as the ich will also reside on the substrate and even the décor. The other treatment can be done using Aquarium salt and raising the temperature by 2 to 3 degrees. Always do water change. And keep the level of temperature the same throughout the treatment.

Swim bladder disease

An Aquarist can easily identify this disease in a fish. The infected fish tends to lose its balance and will have difficulty remaining afloat. This disease is highly seen in Goldfish. There is extra fluid in its body. This disease occurs due to constipation arising out of overfeeding, Intestinal parasites, and low temperature. If not treated in Time can result in another disease called Dropsy. Most of the time this stage results in the death of the fish.

Swim bladder disease can be treated by medicine available on the market. Our go-to medicine has been Seachem Kanaplex and also for the treatment of goldfish an aquarist can feed boiled green peas without their skin to remove the gas.

Fin Rot & Ulcers

This disease is due to the poor maintenance of water quality and injury to the fish.

The fish will have less movement and prefers to stay alone. There will be a loss of appetite.

When the fish has ulcers the visible sign is the feces “POOH”. The color of the feces will turn white. This disease is due to improper diet and low-grade food. Overfeeding and low-quality food, expired food can result in ulcers. The fish generally stays in a corner and will not be active. Always look out for the signs of swollen stomach or even the color of its “Pooh”. Treat the fish by moving into a hospital tank.

Let us check some suggested methods to prevent disease in a tank.

Quarantining the new fish

It is recommended to always quarantine the new fish before its introduction to the main aquarium. Quarantining needs to be done in a separate tank. Quarantine the fish for at least 12 to 15 days. There are products on the market that can reduce stress and get rid of pathogens in fish.

Avoid Overstocking

The general rule is 1 inch of fish per one or two gallons of water not taking into account the décor present in an aquarium. Like people the fish grows too for example Oscar, Arowana, African Cichlids, etc. It’s a tendency to bring in lots of fish not realizing its growth potential. Research your fish well before buying. Even schooling fish needs to move around. Never buy schooling fish in pairs it will lead to stress for the fish. Always buy a minimum of 6 to 8 pairs.

Feed Quality Food / Don’t overfeed

This is the most ignored part by a budding aquarist. Low-grade food will not only have digestive problems in a fish but also will be uneaten and wasted resulting in Ammonia, Nitrite, and nitrate issues. When buying fish food always read the label. Do not go with the picture depicted on the bottle. Every fish has a different requirement for protein. Don’t overfeed the fish. It is ok to feed once or twice a day. Feed as much as per the number of fish present in an Aquarium. 

Water Temperature

Check the water temperature at least once or twice a week. If it’s winter time have heaters in your tank and adjust the temperature. Always buy a quality heater suitable for the size of the tank. Heaters are available in 50W, 100 W, 200W, and 300W. We use quality heaters from Fluval, Beware when buying substandard heaters it can kill your fish due to overheating.


Have proper filtration in the tank. There are many filters available in the market from sponge filters, hang on back, internal filters, and overhead filters. Choose a filter that will keep the tank clean and suitable for the size of the tank. For larger tanks use a canister filter having mechanical, biological, and chemical media.

Prevention is always better than cure.

Author: Sunil Dcosta – Proprietor

( +919821798612

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