Kansan Reef

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Aquarium fish can be affected by disease and sickness

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If you notice you aquarium fish acting or looking different, it may be ill, which can often lead to death. Early recognition of illness is important to restoring your fish back to health.

Like humans, fish are more susceptible to illness when they’re under stress, Hannah Owens, a graduate student of ichthyology at the University of Kansas, said. “They’re just like people. When it’s finals week and your not sleeping and eating right, you get sick.”

“You can’t just call fish sickness one thing,” Owen Hurst, sales manager at Pet World, Lawrence, Kan., said. “As fish’s immune systems become weaker they become more susceptible to more things.”

Fish Sickness Infographic

Sickness among fish can be difficult to diagnose, so close observation is important. “Watch its behavior, is it swimming, is it lying on the bottom, is it eating, is it gasping for air,” Owens said.

There are many different kinds of sicknesses that can affect aquarium fish. Ick, fin rot, popeye, fungus, neurological disorders and parasites are some of the common things that make fish sick, Hurst said.

“Ick is the most common. There hasn’t been a week where I haven’t seen it,” Luke Ballou, aquatics specialist at Petco, Lawrence, Kan., said. Ballou said he’s learned everything he knows about fish illnesses from helping people work out their problems with their fish during his nearly 4 years at Petco. Ick is a parasitic disease that is highly contagious among fish.

Parasites can be harmful because they take nutrients from the food the host fish eat, which leads to starvation, and can cause internal blockage, which leads to digestive problems, Owens said.

Owens researched the relationship of sharks and parasitic tapeworms while working on her master’s degree. “For sharks, it’s no big deal because they’re huge and the worms are tiny and they’ve evolved together.”

Owens said parasites can however be harmful to smaller fish, like those commonly kept in the home aquarium, because they can stress the fish and leave sores where they attach to the fish.

“Sores can get infected and the fish can die from just that,” Owens said, sores can also make the fish’s body less streamline and cause drag, which makes the fish have to work harder to swim.

Physical injuries can come from a number of things, Ballou said, “sometimes they’ll have territory issues or sometimes tankmates beat each other up.” Selecting fish that have similar temperaments will help avoid tank bullying, Ballou said.

Removing over-aggressive and sick fish can help the well being of the other fish in your tank, Ballou said. Ick is contagious so having a quarantine tank is helpful when battling it, Ballou said.

A quarantine, or hospital, tank is a tank that is completely separate from other systems and is usually setup without rocks or sand, just water. This makes it easier to observe and treat sick fish, Owens said.

Medications for Ick and other common aquarium diseases contain copper, which is not reef-safe, Hurst said. This means you’ll have to remove the sick fish from your system, otherwise corals and invertebrates will die, Hurst said.

However, moving an already stressed fish to a new environment can actually be more harmful than helpful for a fish, Hurst said. “The best thing you can do is don’t touch it. Add some salt – do 10 percent water changes every week for a month. That’s it. Don’t touch it,” Hurst said.

“With copper based medications, not only are you changing the chemistry of the water but physically stripping the slime coat off your fish,” Hurst said. While possibly curing your fish of the disease, you’re definitely causing it more stress, Hurst said.

Turning the tank lights off for a few days can help lower stress and restore the fish’s immune system, but it all kind of comes down to survival of the fittest, Hurst said. “We project so much of our emotion onto the fish, it’s hard not to want to do something,” Hurst said.

“It’s sort of sad because you try everything but most the time they end up dying anyway,” Owens said.

“You kind of have to get used to death, which is sad, but they die in the wild. Just try to keep your fish as stress-free as possible,” Owens said.


Author: Chas Strobel

My name is Chas Strobel. I am a journalism student in the William Allan White School of Journalism at the University of Kansas and an avid reef keeper.

One thought on “Aquarium fish can be affected by disease and sickness

  1. I like to heat up the aquarium a few extra degrees and add some salt to the water (ok for most species) This normally cures ick.

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