Photo courtesy of Thinkcage
Your First Fish
Most people who have decided to get a fish tank are very excited about the prospect of starting as soon as possible. Hell, I was impatient too! Try not to succumb to this, however. Many unreputable fish stores that just want to make money will allow you to buy your tank and fish on the same day, but this can lead to disastrous results. A newly setup tank is a very sterile and unbalanced environment for fish (even after the dechloronating water conditioner is added). "Good" bacteria have not established themselves yet and the system is a long way off from being in equilibrium. These nitrifying bacteria will eventually break down harmful products of fish waste decay (ammonia, nitrite and nitrate). However, a new setup does not have any of these bacteria, and so does not have biological filtration capacity yet either. Any new fish you buy will needlessly suffer from an enormous amount of pollution, stress and ammonia poisoning ("new tank syndrome"), especially if they are already stressed from disease and transport--symptoms include gasping at the surface rapidly, clamped fins and other signs of general sickness. A new filter system will only work on a mechanical basis to rid solid fish waste you can see... but fish are hurt more by water chemistry factors that are invisible (even sparkling clear water, in this sense, can be "dirty"). New tanks are best broken in with a little gravel or filter material from a clean, healthy and established tank to bring in nitrifying bacteria. In cycling the tank with fish, buy the hardiest fish first (for example, one or two zebra danios) and let them "seed" the tank, and then slowly introduce other fish over the course of a month or so, taking care not to overpopulate. A lot of people have difficulty believing this advice, and maybe this is one of those things everyone has to learn by trial and error themselves, because seeing is believing. But I have had tanks that were 2 or 3 months old before they established a truly regular pattern. Please note that cycling is an ongoing and dynamic process, and additions to the tank, such as a sudden load of new animals or use of antibiotics (which can often affect the good bacteria in the filter along with the pathogenic ones that cause disease) may cause your tank to undergo a mini re-cycle.
Many new owners are confused by the 1" of fish per gallon maximum rule because they see pet stores greatly exceed this. The truth is that most large pet stores greatly overstock their tanks and some keep their animals in deplorable conditions to save money before they are sold. You should not try to duplicate these tank conditions because these are not kept with any permanency in mind. Pet store owners must account for a huge death rate (up to 90% in some cases) in their tanks from the time they reach their doorstep to the time they leave with the customer, which is part of the reason some of the prices are so jacked up. Most overcrowd to sell the fish as quickly as possible at the least cost, considering their stock is a lot more perishable than say, a few cans of soup. Assuming you the owner, however, are not thinking in terms of a 90% death rate and a 3 week time frame, I would suggest that you try to only duplicate tanks of the show variety (seen at finer fish stores to attract custumers, most are filled with an stable community of fish that are not for sale).
Another big killer in beginner set-ups. Domesticated fish always look hungry once they adapt to the new tank and associate your presence with food. This does not mean that they really are starving, just as a dog who learns to beg for scraps does not always need to be indulged. Stick with the as-much-as-they-can-eat-in-five-minutes rule, or even less, twice a day. It has been shown that animals (and humans too!) that are raised slightly underfed tend to live longer lives, and this involves metabolic fluctuation and fat storage. By this I do not mean try to starve them or just remember to feed them whenever you feel like it. Stick to a regular schedule if possible, and if you have catfish or bottomfeeders (such as loaches, amphibians, crustaceans, etc.) add a *few* sinking pellets every week or so to make sure they are not being out-competed. It is very rare that an otherwise healthy fish will actually die of starvation alone, and if your fish are not eating or getting skinnier, look into the cause of this (most likely disease-related) rather than dumping in more food. Should your tank suddenly get cloudy, this is most likely due to a bacterial bloom. The best thing to do should this arise is to change about 30% of the water, and not feed as much until the cloudiness clears up.
Make Routine Water Changes
Ideally, 20-30% of the water should be changed in a tank every 1-2 weeks. Some new fish owners wonder why we need to change the water so often at all, especially since with fish, plants, snails and running water, shouldn't the system balance itself out as it does in Nature? The truth is that the tank is not at all a mini reproduction of conditions in the wild, because one has to keep in mind that natural systems are probably several thousand times bigger and more complex than any you can recreate. Most of the fish we keep come from river habitats where 100% of the water is exchanged from fresh mountain sources every couple of minutes. Since this is impossible to acheive in your little tank, the water changes you can give your fish and plants will really help them stay healthy and keep pollution (some of which can't be seen by the human eye) at a minimum. No matter what, compounds like nitrates (decomposed from ammonia=>nitrite=>nitrate in the nitrogen cycle, see above) and stress hormones like cortisol will accumulate, which in turn will suppress natural immunity to disease. Water changes are especially imperative when diseases break out, to limit the number of pathogens in the water--in this case, change about 40-50% of the water if possible. I have also found that a water change right before you leave for a 2-5 day trip is an excellent way of ensuring that all your fish will be there to greet you when you come back. In this case, just clean out the tank and filter before you leave. If your fish are healthy to begin with, most likely they will be just fine while you're away (better, in fact, than leaving them in the care of well-meaning but inexperienced friends, who often overfeed).