How to Startup & Take Care of Your Fish
1. Decide whether you want Tropical or Coldwater fish.
Coldwater fish include goldfish and minnows. There are many types of tropical fish, from angelfish to corydoras catfish. Coldwater fish are usually a little more hardy, and will survive those first few mistakes, but they need more room.
Start off with inexpensive fish, they are inexpensive because they are very successful in their natural environments or so comfortable in captivity that they even breed regularly and, in either case, do not die easily on their way to and in pet stores.
2. Decide what kind and how many fish you want.
Research before putting species together. Some fish are compatible, others aren't. One might speculate that fish would enjoy some activity in their lives, so don't get just one.
Make sure you can provide any specialized care the fish need. For example, different fish need different foods, and some fish require more frequent maintenance than others. Owning fish is a big responsibility. Some fish are perfectly happy with flakes and can be fed with an automatic feeder, which makes it possible to leave the tank unattended for a week or two (assuming the fish are small so the water doesn't need very frequent changing).
3. Get an appropriately sized tank. Look up the minimum tank size for each fish.
For goldfish, buy a tank with 20 gallons (75.7 L) for the first goldfish, and 10 gallons (37.9 L) for each additional goldfish.
For freshwater fish, forget about one gallon per inch of adult fish. would you keep a 50 inch (127.0 cm) fish in a 50 gallon (189.3 L).
Tank? Bigger is better. Even if the fish looks small, it will thrive in a bigger tank.
4. Set up the tank and equipments.
Make sure you have all the proper equipment-filters, heaters (for tropical fish), water conditioner, test kit, etc. Put your fish in. Only add a few fish to start with, and slowly build up the population.
Adding too many fish at once can overload your filtration system.
5. Perform partial water changes weekly.
20-30% is a good amount. To do a water change, get a gravel vacuum and siphon out any waste in the substrate. This will pull out water at the same time. Replace the water with water from your tap, but remember to treat it with a water conditioner.
6. Test the water regularly.
Make sure you have 0 ammonia, 0 nitrite, and under 40 nitrate.
7. Monitor your fish.
Feed your fish two or three times a day. While they eat, sit and observe them. Check for anything strange: changing color, falling off fins, damaged tails, etc. Also, make sure all your fish are getting along.
8. Try not to stress out your fish.
This includes putting your hand in the tank when you don't need to, touching them, or jumping near the tank. Try not to make too much unnecessary noise.