THE HOSPITAL/QUARANTINE TANK
It is important to buy an extra tank that is large enough to comfortably house your largest fish, in case it gets sick. Some diseases are contagious, so the sick fish should be separated from your main tank. Some medicines are strong, or may stain the tank, so you should not put them in with your healthy fish. You should also hospitalize the fish if it getting harrassed by the stronger fish in your main tank. Your hospital tank does not need gravel - it does need a place for your fish to hide, because sick fish often want to do that. It also needs a filter and a heater and a thermometer. You will also be using this tank to quarentine any new fish you buy. When you get a new fish, keep it in this tank for about a month, to make sure it does not develop any contagious diseases.
There are many diseases which will remain a mystery to you. Like people, fish can get cancer or kidney disease or anything else. They can also get viruses, which we do not yet have treatments for. However, there are some diseases we can treat. They are common PARASITES, BACTERIAL INFECTIONS, and FUNGUS. It is very important to learn the symptoms of common diseases and to become a careful observer of your fish's behavior and physical appearance. Many diseases that kill pet fish are only minor problems if noticed and treated very early on. It is also important to know what healthy fish look like in comparison, so you can choose healthy fish when you shop. Don't buy a sick fish because you feel sorry for it; the stress from the move to your home may be "the last straw" and the fish will die despite your best efforts. Worse still, you would have introduced a disease into your home that may injure your own fish. Mardel medicines, and many books, contain flow charts to help you diagnose and treat your fish. Read the descriptions of diseases below. Also, my LINKS page will also lead you to the forums and help you need.
It is wise to visit pet stores and study the health of the fish: they are often selling sick fish and you will learn to tell a healthy fish from a sick one, and notice the different symptoms of different diseases. Some signs to look for are white spots on the fish (Ick), slime hanging off of it (a few bacterial infections cause this one; one, called "body fungus" is not a fungus at all, it is a bacteria), swollen gills and hanging near the surface (the fish can't breathe and is looking for extra oxygen - "gill disease" has a few possible causes), flicking off of decorations (the fish feels itchy - early warning of parasites like Ick), sulking in a corner when it used to be active, weight loss, trails of feces, bloat, weird swimming behavior (lots of causes, probably an internal bacterial infection). The important thing is to never buy a fish that looks this way, and watch your own fish carefully every day to catch problems as early on as possible. Don't let small problems become big ones by not noticing until it's too late.
With luck and good tank hygiene, you should not need medication for your fish often. However, fish do get sick -- when stressed they are vulnerable to infections of parasites, bacteria, and fungus.
Parasites are a common problem. One medicine to have is Aquarisol. This product helps PREVENT common parasite infestations that can kill all of your fish in a short time. "Ick" or "Ich" is the most common parasite - it is deadly and very contagious and often found in pet store tanks. This is why it is very important to check fish for signs of this disease (white spots) before you buy them and DO NOT BUY A FISH THAT APPEARS HEALTHY IF ANOTHER FISH IN THAT TANK IS SICK OR DEAD! Most diseases are very contagious, and that new fish may die and may help to kill the ones you have at home. For this reason it is important to put all new fish in your "hospital tank" for quarantine (about a month) to watch for disease outbreak before you put the new arrival in with your established community. I use Aquarisol in the quarantine tank to help keep the new, stressed fish healthy. If you do have a fish with an advanced parasite infection, remove it to your hospital tank and treat it with Quick Cure or Maricide.
Bacterial infections are also common, and occur both internally and externally. An external infection, for example fin rot (frayed fins) or red sores, can be treated with Melafix. Internal infections, like dropsy (which makes the fish look bloated) or infections that make the fish hollow-bellied, skinny and wasting, are more difficult to cure; you can try Mardel's Marycin products or Triple Sulfa drugs, or "AP Plus Anti-Bacteria". Refer to your disease charts and established web forums to diagnose and treat your pets. It is interesting to note that it is less expensive to put medicine in the food than in the water.
The third type of disease is true fungus, which is fluffy white growths that attack dead tissue at sites of injury. This can be treated with MarOxy. Note that some diseases, especially mouth fungus, look like fungus but are in reality bacterial. Check your books and charts.
When asking for help from a web forum, give the group as much information as you can in your FIRST post. What are your tank conditions (When did you last change the water? Have you tested the water? Is there ammonia or nitrite or nitrate present, if so, how much? Is the pH or KH wrong or has it changed recently?), How about your fish's behavior (is it hanging and not swimming? Is it flicking itself against ornaments like it's itchy?), What is your fish's appearance (is there white slime hanging off of it or white spots on it or are the gills open and swollen?), and give the fish's recent history (was it moved, or stressed by a change in temperature?). The more information you give, the faster they will be able to help you.
"An ounce of prevention is worth a pound of cure." To keep your fish healthy, do not overcrowd them (for small fish, one inch of fish per gallon is a good rule of thumb, less is better), keep the tank clean, change part of the water (20% per week is good), and keep all the parameters stable. Fish hate sudden changes in the water - the temperature, pH, hardness - all should stay stable when you make your water changes.
The greatest cause of fish death in aquariums is overfeeding. Uneaten food rots quickly and poisons the water with ammonia and nitrite. When you feed your fish, WATCH THEM EAT. If they can't eat it all right away, take the extra out and feed much less the next time. They can do just fine with little food. They will die with too much. Check your water temperature every day to make sure the heater is set and working properly. Analyze your ammonia and nitrite levels often. Take good care of your biological filter (read the filter section). If you take good care of your tank, a massive die-off from disease is unlikely.
FILTERS AND STUFF
THE NITROGEN CYCLE
DISEASES AND MEDICATIONS
PLANTS AND ALGAE