Like any other pet even aquarium fish gets sick and every beginner aquarium maintainer needs to know what to do when fish gets sick. Before you can do anything about their sickness you need to know how they eat, how they look and swim before you jump to conclusion that they’re sick. If you manage to recognize some change in their behavior then you’ll be able to tell that easily.
There are some signs of illness which are pretty much same for all types of fishes.
Movement
* Normal bottom fish dwelling at surface
* Normal hiding fish coming out often and is quite visible instead of hiding
* Scratching on objects of tank
* Trying to jump out of tank
* Lying to bottom and gasping
Eating
* Loss of appetite
* Heavy eater but not interested in eating
* Losing weight even though eating
Breathing
* Squirting water
* irregular opercular beat
* Something stuck in cavity or throat
Color
* Change of color either dark to light or light to dark
* White or gray sheen on skin
Tank
* Filter/Air support equipment not working properly
* Faulty filter/Air equipment
* Filter part/Specimen broken and decaying in tank and fouling tank
* Protein foam on surface of water
* Excessive food in tank
* Cloudy water
* dying plants
Other health signs & taking action
If your fish is swimming slowly or have clamped fins or behaving in a way other than known habit then most likely this could be the problem related to ph level. You need t check the ph and have to maintain it and if possible you can remove that fish into another small pond for a while.
When it comes to parasite infection you;ll notice string like or substance like thing attached to the body of fish. Adding potassium permanganate of about 10ml inside water will kill parasites. In between you can take those infected fish to another small bowl just in case if you want to remove remove parasites with potassium permanganate.
Bacteria infection is serious and you’ll see it as affected every fish in the tank. You need to know what type of infection it is before you take any action for tank water. Depending on the level of tank infection you can add antibiotics in the water.
When it comes to ich infection, there appears to be white spots on the body of fish. There are various ich treatments available in aquarium shops so depending on the level of infection you need to take action. Most likely even if one fish gets infected you need to quarantine whole tank as other iches likely to be present in the tank.
Any change in behavior from known is likely to be health related issue. You need to take action before the die or any infection spreads in the tank. If in doubt always consult with aquarium shopkeeper and veterinarian about any change in behavior or health related symptoms. Other than that you can look-up on this hub’s general advice to check for any signs related to fish health.