What Causes Disease?

[DebraAustin]

I'm very new to fish keeping and read all these horrible stories about awful sounding diseases that people are dealing with like ick and hole in the head, etc. If you get a healthy fish to begin with (which I know is more than half the battle) what causes disease? Is it water quality? I would like to know more about the conditions that create ill health in fish, so that I can do my best to avoid them. Anyone got info they'd like to share?

Debra

 

[Teelie]

The main way fish get sick is stress. What causes the stress though is a multitude of things with the main causes of stress being the water quality, tankmates and sometimes the diet (improper feeding habits lead to starvation or getting too fat). Most of the time the immune system of the fish is able to fight off infections. When the balance is upset and the fish get stressed out though, their immune systems are among the first things to go downhill. The same goes for humans. Something to keep in mind.

"Food poisoning" is about the only thing not somehow stress-related to a fish getting some disease. Usually when food is responsible for a sick fish, it's live or once living (frozen or recently killed) that was sick with a bacteria, virus or parasite that infects the fish.

This of course excludes parasites like hookworms and flukes (amongst others) which often come from dirty or unsanitary keeping conditions usually at a supplier (the people who sell the fish to the LFS and chainstores). These things are normally only a real concern involving wild caught fish who've been caught from who knows what kind of living conditions. Tank raised fish should never have contact with these kinds of parasites under normal circumstances.

Of course there are exceptions but that's generally the case IME.

 

[Trance2006]

Well this is coming froma 16 year old.

Disease in tropical fish is usually caused by stress. Along the lines of you loveing to spook the fish way too much, injury, bad water quality, ammonia, chlorine, Nitrite, and huge high levels of Nitrate.

Ick or white-spot disease is usually the most common. I have found saltwater baths help FW fish whilst freshwater baths help SW fish drop the ick.

Hole in head or lateral line disease is one that not many people can understand. There is one good theory that stray electrical currents in the aquarium cause it but I don't believe that.

There are a lot of books you can purchase, also I think we have a section on it in the forums. Also make sure to check the emergency section. You will learn a lot of diseases that way.

 

[Tempestuousfury]

There are many different causes of fish illnesses.

They are mainly caused by fungus, bacteria, viruses, protozoans, and poor water quality. Adding new fish without quarantining them can result in outbreaks if the fish have contagious disorders.

The greater the stress on the fish, the greater the chances that the fish will succumb to a disorder.

In general, the best way to prevent these disorders is to quarantine new fish for about a month, keep the water in good condition, feed sparingly, and isolate sick fish and treat the disorders as early as possible to prevent more outbreaks and increase the chances that the afflicted fish will survive.

 

[annka5]

I agree with the above. The obvious cause is bacteria, parasite, or the like. However, fish are usually well able to fight these off without becoming ill - it's only when tehir immune system is compromised that they will fail to fight them off and fall sick.
Stress is caused by poor tank cleanliness, tankmates, tank size, tank decor, temperature, inappropriate water conditions, food, old age, etc etc. It's a long list of things which can cuase it; however if you set the tank up and choose its' occupants carefully then you wouldn't expect issues.

 

[Bignose]

As a forum member who has spent a lot of time debunking some of the common myths, I think it cannot be overemphasized that the root cause of almost every disease is a parasite or bacteria or fungus. Case in point, there are a lot of people who may tell you that ich is in all water, which is absolutely false.

That said, if there is a very small population of parasite, fungus, or bacteria, and then the fish is stressed, that is when the fish's immune system starts losing. Several of the books I have note that at least 95% of problems occur due to poor water quality. Poor water quality weakens the immune system, and then the parasite, bacteria, or fungus may attack the fish unchecked, reproducing quickly until it gets out of hand.

A really good analogy is the advice your mother gave you to wear your coat in the winter, or you'll get a cold. Just being out in the cold cannot cause a cold virus to spontaneously appear in your lungs. But, when your friend coughed and you inhaled that cold virus, your immune system may have been weakened because you were out in the cold without a coat. The cold did not cause the virus, but it did give the virus an entryway into your system.

So, on the one hand, the primary cause of the disease has to be in the tank in the first place (very good reason to quarantine, eh?). But, then, even if there is a tiny infection, the fish may live a very long and content life until its immune system is stressed. In my mind, the moral of the story is quarantine and stress-free.

 

[DebraAustin]

Thanks for all the information. So, it seems that I can give my fish the best chance by keeping their lives happy and their water clean. I'm working hard to attain both and so far so good.

Debra