Diagnosing Fish Diseases: When NOT To Treat
by: Lennart Edén
The most powerful tool in diagnosing disease in humans is the anamnesis, the patient's own description of the ailment. This tool is largely unavailable to us when diagnosing disease in fish, or other pets. The only way the animal can directly convey information to us is by its behavior and appearance. If we have a good picture of its normal behavior and appearance any aberration can provide us with vital proof, or at least hints, of the underlying course. Other possible sources of information are tissue samples and slime smears, fecal examination etc. To obtain and evaluate the information and make a reasonably certain diagnosis you would, in many cases, need a level of skill and knowledge that can seldom be said to lie within the scope of the average hobbyist. This means that an alarmingly large percentage of any "cure" administered by fish hobbyists is directed against the wrong causative agent. To add to the problem, many of the available medications are poorly researched in our context of fish keeping, to put it mildly, the accompanying information is often of mediocre value and/or inaccurate and the medication is often administered by us hobbyists in a less than satisfying fashion. We should also remember that many infections are only secondary and that the primary causative agent must also be identified and taken care of.
When treating with antibiotics it is very important to follow any instructions for treatment that are given. Most important, is to follow the treatment through and not cutting down the time of the treatment program, be it out of some concern or because you see an improvement. In the process you may be breeding a relatively easily treated bacteria into a resistant killer strain. Given the large number of pet owners who have access to and use antibiotics and the very real danger of creating resistant strains of bacteria that may prove pathogenic to our own species, a total world wide ban on antibiotics for use on pets may lie in the not so very far future. Fortunately there are some common diseases in fish that are fairly easy to diagnose, given some experience. This doesn't necessarily mean that we should immediately bring in the heavy artillery. It is indeed dangerously tempting to use any medicine you have at hand to "save" your suffering pet. Unfortunately, we often end up killing them instead.
The most important instigative factor in fish disease is no doubt stress. This factor in it self could have many underlying causes, many of which can be influenced by the hobbyist. Water chemistry is, of course, the all-encompassing concern. Keeping the water clean and the water parameters stable is a never ending duty and challenge and a key factor in keeping your fish healthy and thriving. There are a few fairly safe measures that can be taken to improve the chances of recovery in an ailing fish even if you are unable to make a positive diagnosis.
A slight increase in temperature in the tank will speed up the immune system of your fish. Raise the temperature *slowly* to 82-86°F (28-29.5°C), maybe even as high as 90°F (32°C), but watch the fish closely for any signs of distress. Remember that warmer water can carry less oxygen. Most bacteria, and especially some pathogenic bacteria, do not respond well to increases in temperature. Some may increase their activity but very little when compared to cells in higher organisms. This is one of the reasons we get a fever when the body is fighting off an infection. The white blood cells responsible for much of our defenses are able to increase their activity much more than the bacteria (or viruses). Our fishy friends don't have our ability to raise their body temperature the way we can so sometimes we have to help them fight an infection by raising the tank temperature.
In some instances a small addition of salt will be beneficial too. You don't have to avoid iodized table salt, that's just another myth.
Beware that all fish can't tolerate high temperature or salt.
Filtration with a sub micron media, such as diatomaceous earth, can filter out free-swimming parasites. A DIY alternative is using a sub micron filter insert from a vacuum cleaner in your regular filter. The media will clog fast so you may have to change or clean it several times.
Filtration with a UV-filter will kill anything small and suspended in the water and will relieve the pressure on our fish from many primary and secondary infectious agents.
Preventative measures are much more effective than treating fish that are already sick. Try to provide an environment for the fish that is as free of stressful factors as possible. By following a few basic rules you can limit the risk of fish disease significantly.
Only buy good healthy stock. Buying cheap fish from disreputable dealers will often turn out quite costly.
Use a quarantine tank. For quarantine purposes I have a permanently set up 20 with gravel, fast growing plants, good lighting, filter, heater etc. Basically it's set up the same way as I would set up any tank. It has a bunch of Guppies of varying sizes as residents that can be easily moved to other tanks when buying new fish.
Isolate sick fish. In case of a medical emergency I have an assortment of plastic tanks and barrels that could be used. For this purpose I keep a small power filter running in an established tank to keep it seeded with bacteria. If need be this filter could be moved to a plastic tank that could be filled with water from an established tank. I would add some fast growing plants like Hygrophila polysperma that can grow without a substrate, good lighting and a heater. With frequent small water changes I think it would work out nicely.
Never mix incompatible fish. Even if they don't fight some individuals may experience enough stress to make them susceptible to disease.
Keep your plants healthy and growing - A planted tank with good growth will always be more stable and healthy than a bare tank.
Get your lights on a timer and keep them on for 10 to 12 hours per day. Growing plants will consume nitrogen and help keep the water clean. They will provide hiding places and cover for your fish and a fairly large surface area for the good bacteria that will convert toxic ammonia into less toxic nitrite and then into the least toxic nitrate. Give the plants a good nutrient supplement, (trace elements) like Tropica Master Grow, and some substrate fertilizer, to give them an edge over algae. If the plants grow well the algae will have a hard time. Keep surface agitation down to preserve CO2, which the plants need to grow. If you have an air stone or such, remove it as it will drive out CO2 and will not oxygenate the water. If you have a tight cover on your tank you can let the air hose, or a small fan, blow fresh air under the cover. Algae problems are seldom caused by too much light but most often by a nutrient imbalance.
Keep the water clean - It's better to take the money you intended for your medicine cabinet and invest it in a better filter.
Make regular water changes. There is no way around it. Small frequent water changes are better than large water changes less often.
Get to know your fish.
Read as much as possible. Fish keeping is all about experience, balance and patience. And knowledge of course, but don't believe everything you read. When in doubt, ask questions and confirm the answers.
Keeping a log is invaluable. It will allow you to go back and look for correlations between observations made by observing your fish and any changes that has been made in the tank.
A special word of caution; mixing two different medications is a *very* bad idea. There is no way of knowing what interactions may occur. If you need to get rid of any added chemicals, first make a large 25% water change and proceed to make several small (3-5%) incremental water changes over the next few days. You could add activated carbon to your filter to get rid of any remaining chemical compounds from the medication but if you keep up with the water changes I don't think this is necessary.
In the past twenty years I have only used medications on two, maybe three, occasions. Looking back I could probably have done without.
Pet medicine is a very lucrative business, but hardly because we really need all these potions to keep our pets healthy. All in all, I think the only good medication to keep in your medicine cabinet is *knowledge*. Leave the potions on the shelves at the LFS.
Subject: Diagnosing Fish Diseases: When NOT To Treat 
Sun Jul 22, 2007 1:14 am