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What Makes an Aquarium Fish Sick?

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How to Maintain Water Quality in Your Aquarium

How to Prevent Aquarium Fish Illness

The best way to handle health problems in fish is to prevent them from happening in the first place. By purchasing healthy specimens to stock your tank, quarantining and acclimating all new arrivals properly, and keeping a close eye on your fish for signs of potential sickness, you can reduce the likelihood of disease in your aquarium— or at least catch a sickness early, when it is most easily treatable.

Purchase Healthy Fish

As with any animal, it’s important to pick a healthy individual when selecting fish for your aquarium. Starting out with a healthy specimen makes it much less likely that your fish will succumb to illness in the future. When examining prospective fish, look for the following characteristics:

Clear, well-shaped head
Fins that are in proportion to the body
Good body shape and skin quality
Lively, energetic behavior
No signs of illness, injury, or parasites
Straight spine

No fish is perfect; they all exhibit good and bad qualities, though the merits of purchasing the best-quality fish available invariably outweigh any faults an individual may have. Even fish with minor abrasions and splits in the fins can mend with proper care, but beginners should purchase fish that are as healthy and unblemished as possible.

Quarantine and Acclimation

Whenever you bring home a new fish, and especially if you’re introducing a new fish to an existing aquarium, that fish must adjust to its new environment. All fish need to be acclimated to water that is different from that in which they’re used to swimming, and those added to an existing tank should be quarantined for several weeks beforehand. Without this period of adjustment, the fish could face serious consequences, ranging from social difficulties with new tankmates to death from the chemical shock of unfamiliar water conditions. Also, your new fish could be carrying an illness or parasite that could infect your other fish.

How to Quarantine Your Fish

When you first acquire any type of fish to add to your existing aquarium, keep it by itself for a month after you bring it home, without sharing a water source with other fish. During that time, any disease it might be carrying will likely manifest itself, and you can treat the fish to eliminate the infection.

Also, remember that fish don’t have to come into contact with one another to spread disease. Nets, hoses, or even your hands can transfer pathogens from one container to another. And keep in mind that even a properly acclimated fish can be so stressed by suddenly entering into a new environment that the experience can kill it. After several weeks of quarantine, you can be certain that your new fish is healthy, has adapted to your water and food, and has recovered from the stress of transport and sale.

How to Acclimate Your Fish

Acclimating a new fish requires you to match the conditions and chemistry of the water in which the fish has been swimming to the water in the tank in which it will live. Acclimation is absolutely necessary for all new fish. If the chemistry of the water in your aquarium is drastically different from that of the water in which the fish arrived, the chemical shock can kill the fish outright or weaken it so badly that it succumbs in a short while. The proper acclimation of a new fish not only keeps it from receiving these severe shocks but also prevents the introduction of any diseased organisms or unwanted chemicals into your system.

The following method of acclimation takes a little time but only requires a container and some airline tubing.

Gently empty the bag in which your new fish arrived into a container that can hold several times the volume of the original water in the bag.
Tie a loose knot in the length of airline tubing.
Put one end of the tube into the aquarium, and suck on the other end to start a siphon.
As soon as the water begins to flow through the tube, tighten the knot until the water is merely dripping slowly from the tubing into the container. (You want just a drop or two to escape per second.)
When the volume of water in the container has doubled or tripled, stop the drip and net the fish out of the container, then release it into the tank. Dispose of the water in the container down the sink drain. Do not put it into your tank.

This method equalizes all water conditions, including temperature, between the aquarium and the water in which the new fish has been swimming. It takes a while, but it’s time and effort well spent. You can now safely add your fish to its new home.

Monitor Your Fish

Paying regular attention to your fish and their behavior patterns will make you more aware of small changes that may be the first warning signs of illness. Though many diseases have their own unique symptoms, there are also several general signs of illness that a sick fish may exhibit. If you notice any of the following symptoms in your fish, it’s likely due to a health problem.

Bloating or emaciation
Folded or clamped fins
Hanging from the surface of the water
Lesions, spots, or bumps
Loss of appetite
Loss of luster
Lying on the bottom of the tank
Pale gills (instead of a healthy red color)
Ragged fins
Rubbing against surfaces (“glancing”)
Slow reaction to disturbances
Sluggish or aimless swimming

Acknowledgments & Disclaimer

Previous:
What Makes an Aquarium Fish Sick?

Next:
How to Maintain Water Quality in Your Aquarium

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