Many people have the concept that the aquarium is a sterile and safe environment, and that safety seal is temporary opened when you add new fish and plants into it. After that if your fish continues to be fine and healthy, then no baddies like disease or parasites or bacteria has breached the castle, until the next time you introduce new fish into your aquarium.

In fact, that concept is very wrong!

All fish carrys bacteria/parasites on their body, and indeed all aquariums contains harmful bacteria and parasites. This is the same case as us humans. We carry millions of bacteria and parasites (ie dust mites) on our hair and skin. We pass them around when we come into contact with one another and when we come into contact with the things around us. Look at our cash and coins. They change hands from one person to another. Along the way, it has definitely ever come into contact with even strongly contagious diseases. And they never gets washed! When is the last time you wash your dollar notes? And do you know there are people who put coins in their ears until they need to use them? In fact, the only time money gets a rinse is when someone accidently drops them into the toilet bowl, after with the cleaner digs it out with his mop that he use to clean the toilet bowls as well as the taps you wash your hands with. Ok I think we’ve sidetracked enough, but I guess you get the idea. Humans and fish actually lives with bacteria and parasites as part of our everyday life.

These bacteria and parasites are kept in check from doing the harm they are capable of by our body’s and our fish’s own defense mechanisms. They are harmless unless the conditions becomes favourable for them, thats when they can cause serious trouble.

Look at humans, our defense is down when we suddenly put ourselves in very cold environment without proper clothings. We can also get infections when we get physically wounded.

For fish, they are also very similar.

Fish’s defense is down when:

• Fish is under stress, causing the immune system to be down
• Poor water conditions such as sudden changes in water conditions or water parameters
• Physical injuries such as bites or scratches.

If left untreated, a sick fish acts as a fertile base for these bacteria/parasites to multiply in large numbers. As a result, the infection gains power and this infection then spreads to other tank mates. Over time, your tank becomes a death trap killing everything in it.

Disease prevention

Prevention is better than cure, and these words of wisdom are never more true then when it is applied to fishkeeping. When you get a disease, the first headach is identifying the disease. A wrong identification will not only waste your time and money in giving it the wrong treatment, it may even make matters worse. Other than that, medication can harm your biological filter, and it can can trapped in your porous filter media, permanently wrecking them.

If you didn’t skip the section above, you’ll know that the best way to fight the war against terror is to keep your fish in their best conditions and help their immunity systems do what they do.

1. Ensure the water condition is kept to the ideal level.

• Maintain your filtration system so that ammonia and nitrites is kept at zero level.
• Test your water with test kits at the first signs of trouble (ie fish behaving abnormally, inactivity etc). Check for pH levels and ammonia, nitrites and nitrates to see if they are under control. Early detection of these problems give you a chance to rectify things easily before it gets tricky (ie fish falls sick).
  pH can be easily adjusted if it got too low or high
  ammonia or nitrite spikes can be easily diluted by water change (after which your filtration system should be analysed to see what went wrong.)

2. Don’t accidently add already sick fish into your aquarium.

To spot sick fish in the fish shop, sick fish usually have the following symptoms

• abnormal swimming style (such as tailspin, rapid/jerky movement or misalignment).
  In a fish shop, it is usually easy to spot problem fishes if you look at the whole tank without concentration on one single fish. These fishes usually do not move the same way with other fishes in its tank.

• Signs of injuries to fins and body.( such as bleeding, ulcers, skin or fin tear)
  Skin/fin tear are usually caused by territorial fish fighting with one another. In most cases, these injuries can heal rapidly. However, in such cases we should think about its injuries and why it is injured. Aggressive fish often fight and cause damage especially in a small enclosed environment. If only one fish in the tank is injured but the rest of the fish are relatively injury-free, then that fish may have been picked upon because it is already weakened by some kind of sickness and the other fishes have sensed it.

• Appetite lost( ie not eating )
  A healthy fish will devour any food without much thought. A loss of appetite in the short term when a fish is introduced into a new tank is normal. This is due to the stress of new, unknown surroundings for the fish as well as a new feeding pattern by different keepers. However, if a fish is to suddenly stop eating in the same tank it has always been in, it is highly possible that it is sick. If you are aquiring an expensive fish or if you know the fish store well, you could request to see the fish eat before buying.
  (note: Be tactful! Don’t say ‘”I wanna see your fish eat because I think it may be sick.” Instead say something like “I love to see fish eating.. can I feed this one?”.

• Blur eyes, pop-eye or white spots on fins and body, or any abnormal growth or redness on the body or fins.These are obvious signs of already sick fish that require immediate treatment and you should not get these fish nor any fish in the same tank. Personally I would run far far away and not turn back until it is safe to do so.