--Introduction--
Since even a small amount of material can be difficult for a newcomer in any field to digest and retain, the novice aquarist may wish to read only the ``Good First Fish'' section to begin with. Then, while consulting a good beginner's book (the most essential item for any novice aquarist to own), she or he should choose a small number of possibilities for the fish with which to start her or his new tank.
If someone familiar with the local fish stores is available, it is wise to get a recommendation for where to shop for fish. Otherwise the beginner should try looking for shops that specialize in fish, either exclusively or as a major part of their business. This is no guarantee, of course, but it does improve the odds of finding a good store.

If, upon reaching the store, none of the selected fish can be found, the novice should refrain from purchasing any fish that he or she is unfamiliar with, even if recommended by the store's employees. (Some stores have very knowledgeable staffs but many, alas, do not. It will take some time before the new fishkeeper can discern a good store from a bad one, or good advice from poor.) At this point, another store could be sought out or further reading done to determine alternate choices for first fish.

Assuming that desirable choices for first fish can be found, the beginner should carefully inspect the specimens for sunken bellies, sunken eyes, clamped fins, labored breathing (often with gill covers quite extended), and any sort of external blemishes that might indicate parasites or disease. If the fish appear healthy, the novice should ask to purchase a very small number of fish, depending on the size of the tank and the fish. A twenty gallon tank is a good size for a beginner; it is large enough that the water conditions will be fairly stable, yet small enough that the beginner is not intimidated. For this size tank a single fish of one to two inches in length, or three or four smaller fish, is the most the novice should start with. (If more fish are put into the tank initially, poisonous ammonia will build up and kill the fish. If the tank population is built up gradually, however, this will not be a problem. To understand this gradual introduction of fish, known as `cycling the tank', the novice should read about the nitrogen cycle in his or her aquarium book, or the NITROGEN CYCLE section of the BEGINNER FAQ.)

--Good First Fish--
If we define a good beginner's fish as one that is easy to feed and care for, hardy, able to live in a variety of water conditions, and attractive, then there are a number of widely available fish which fit the bill nicely. Many of these are regularly sold as beginner's fish. But watch out! Many of the fish sold as beginner's fish really are not well suited to that role.
Many of the smaller schooling fish make ideal first fish. These include White Cloud Mountain Minnows, the several commonly available species of Danios and Rasboras, and most available species of Barbs. For those with a slightly larger tank, Rainbowfish make a great schooling fish. Corydoras Catfish are ever popular schooling catfish.

While many beginners are tempted to get just one or two of each of several different schooling fish, this should be resisted. Schooling fish do better if there are several of their own species present for them to interact with. A minimum of six of each of the midwater schooling fish is recommended, while four is the bare minimum for Corys. In the long run, a school of a dozen fish showing their natural behavior will be more pleasing than a mixed group of fishes unhappily forced to share the same tank. (``Mom, why is that one fish hiding behind the heater and that other one just hanging in the corner?'')

Of course, as mentioned in the introduction, the population needs to be built up slowly, two or three fish at a time. The aquarist might, for instance, build up a school of eight Rasboras of a certain species, then turn t

Q: Why is my fish sick and how do I prevent more illness?

A: Probably 80-90% of diseases in captive fish can be prevented by avoiding stress. Stress weakens fishes' immune systems, leading to increased susceptibility to disease. Actually, diseases and pathogens are almost always present in tanks, but a healthy fish's immune system will prevent them from being a problem. Some of the most common stressors for captive fish are:
Poor water quality: measurable ammonia or nitrites, or very high nitrates.
The water temperature is fluctuating more than 2 deg F/day
Incompatible species in the tank.
Too many fish in the tank (5 adult angelfish in 10g tank).
The tank is too small for the fish (foot long fish in 10g tank).
The water is too warm or too cold for the species (goldfish vs. tropicals).
wrong pH for species (Discus vs. African cichlids)
pH fluctuations greater than 0.2 units/day.
Insufficient cover or hiding places present.
Wrong water hardness for the species (Discus vs. African cichlids).
Insufficient oxygen in the water.
Improper fish nutrition (wrong food, foods not varied).
Keeping your tank free of disease

Q: Do I need a quarantine tank for new fish?

A: Quarantining new fish is a good habit for all aquaria, but is not absolutely necessary for success. Quarantining is simply keeping a fish in a separate tank for long enough to be certain that it is disease free. Many beginners do fine without a quarantine tank, and object to the cost of another setup. A quarantine tank does cost more, but if a hobbyist has hundreds of dollars invested in fish, it is cheaper to have a separate quarantine tank than to replace fish killed by a newly introduced disease. Also, many of us become attached to fish and do not want to expose our pets to diseases from newcomers, no matter what the cost.
The purpose of quarantining is to avoid introducing new diseases to a stable system, and to be able to better observe new fish for signs of disease. A quarantine tank can also double as a hospital tank for sick fish. Hospital tanks are good because they lower the cost of using medicines and keep diseased fish separate from healthy ones. Quarantine is probably most important for saltwater tanks/reef systems because of the difficulty of treating diseases, or wild-caught freshwater fish because they are probably not disease-free. Quarantining itself can stress fish so be sure quarantine is as stress-free as possible.

To set up a quarantine or hospital tank:

Keep an extra filter -- a sponge filter is ideal -- or piece of filter floss in an established tank, so that you don't have to keep the quarantine tank set up at all times. Some people choose instead to keep the filter going with guppies or danios (for freshwater) or mollies (for saltwater).
If you don't keep the tank running, use old tank water to fill the tank. So: old tank water + established filter = instant established tank.
Add a spare airpump and heater. If you haven't messed with the heater during storage, it should come to wherever you had it last time.
Consider using Amquel or equivalent when medicating the tank in case the biological filter bacteria are sensitive to the medication. Sick fish are especially susceptible to ammonia. (Note that ammonia which has been bound with Amquel still shows up on a nessler ammonia test. So, if you are planning on testing for ammonia in that tank, you need to use a salicylate ammonia test.)
For a hospital tank, do small, frequent water changes (even every day).
If possible, quarantine all of your new fish for about three weeks. During that time, gradually acclimate the fish to your tank's parameters: hardness, pH, salinity, temperature, etc., and watch for and treat any signs of disease.
Do not medicate quarantined fish ``just in case.'' Only treat evident, definitely identified diseases. Treating all quarantined fish with a bunch of medicines will just lead to weakened fish and antibiotic resistant