A starting guide. Read more than this page before the first aquarium. Maintenance foods and supplies that we stock in Square are linked below. Prices live on those product pages.
Equipment
Air pump if a filter needs one, or an air stone to hold oxygen. An algae scraper. A tank big enough that a beginner is not fighting a tiny box. A stand that can hold about 10 pounds per gallon. A background. Two buckets. A dechlorinator that handles chloramines. Food that matches the fish. A heater, a thermostat, and a separate thermometer at the opposite end. Mechanical, biological, and chemical filtration sized to the tank — read about cycling before you buy a filter that is too small or more than you need. A lid, easiest with the lights included. A siphon. Substrate. A test kit for ammonia, nitrite, and nitrate. A timer on the lights.
Setting up
Rinse the tank, gravel, and decorations with no soap. Level the stand. A 20-gallon tank can weigh about 200 pounds once it is full. Fill it, then run it at least 24 hours before you add fish so you can set the heater, air, light, timer, and filter and watch the temperature. A dechlorinator belongs in at this point. Tap water is usually fine. Some people use bottled water.
Cycling
Give the beneficial bacteria time or the first fish die of new-tank syndrome. One way: a small group of sturdy schooling fish such as danios, plus a bottle of nitrogen-converting bacteria, and media they can colonize — plants, gravel, a sponge you never wash in hot water or detergent. Test ammonia, nitrite, and nitrate. They spike, then fall. Cloudiness is normal. Small water changes and small feedings while it cycles. At least two weeks. Then add fish slowly. A few fish, then wait weeks before the next group.
Adding fish
Temperature and pH are the gaps between our water and the bag. On a new tank, float the bag 10 to 15 minutes, poke a hole, wait another 10 to 15 minutes, then release them. On an established tank, put the fish and their water in a bucket and drip your tank water in through airline tubing with a loose knot to slow the flow. When the bucket is more of your water than the store water, net the fish in and leave the bucket water out. Top off. That drip is also a water change.
Maintenance
Feed two or three times a day, only what they finish in about five minutes. Pull uneaten food, dead fish, and plant debris. Check the thermometer. About 25% of the water each week on a basic tropical setup. Replacement water must not be cold. Dechlorinate tap water. Scrape the glass. Vacuum the substrate. When you rinse mechanical media, do only half, in water at the tank temperature or a little cooler. Hot water and any detergent kill the bacteria. Unplug equipment before you put your hands in the water. A running heater exposed to air can crack.