What you need to start an aquarium

A working aquarium requires a tank, a filter, a heater (for most fish), lighting, substrate for the bottom, and water treatment chemicals. You also need a way to test water quality — at minimum, a kit that measures ammonia, nitrite, and nitrate. The tank itself is the largest expense, ranging from $50 for a 10-gallon glass tank to several hundred dollars for larger or specialty tanks. Everything else — filter, heater, lights, substrate, test kit — typically costs $100 to $300 combined, depending on tank size and the quality you choose.

Beyond the equipment, you need to understand the nitrogen cycle, which is the biological process that keeps fish alive. Ammonia from fish waste builds up in the water. Beneficial bacteria convert ammonia to nitrite, then to nitrate. This takes 4 to 8 weeks to establish in a new tank. During this time, the water is toxic to fish, so you either need to cycle the tank empty first or add fish slowly and do frequent water changes. Many beginners skip this step and lose fish within days.

You will also need a gravel vacuum, a bucket for water changes, and a net. These are inexpensive but essential — you cannot maintain water quality without them. Plan to spend 30 minutes per week on maintenance once the tank is running.

Key Takeaways

  • A basic aquarium setup costs $150 to $400 total, with the tank being the largest single expense.
  • The nitrogen cycle takes 4 to 8 weeks to establish, and fish added before it completes will likely die.
  • You need a water test kit to measure ammonia, nitrite, and nitrate — guessing by appearance does not work.
  • Weekly maintenance includes partial water changes, filter cleaning, and checking that equipment is running.
  • Tank size matters more than most beginners think: smaller tanks are harder to keep stable and require more frequent water changes.

Choosing the right tank size for your situation

Tank size determines how much work the aquarium is and how forgiving it is when something goes wrong. A 5-gallon tank swings between too hot and too cold quickly, and ammonia spikes fast. A 10-gallon tank is the practical minimum for a beginner. A 20-gallon tank is easier to maintain and gives you more options for fish species. Anything larger than 40 gallons requires more space and stronger equipment, but the water stays more stable.

The shape matters too. A tall, narrow tank holds the same volume as a short, wide one, but the wide tank has more surface area for oxygen exchange and is easier to clean. Avoid tanks taller than they are wide unless you are specifically keeping fish that need depth, like discus or angelfish.

Where you place the tank affects its stability. Direct sunlight causes algae blooms and temperature swings. A spot near a heater or air conditioner creates temperature stress. The best location is away from windows, away from vents, and on a sturdy stand that can hold the weight — a 20-gallon tank filled with water weighs about 170 pounds.

Filter types and what each one does

The filter removes waste and grows the beneficial bacteria that keep the tank safe. There are three main types: hang-on-back filters, canister filters, and sponge filters. Hang-on-back filters are the cheapest and most common for tanks up to 40 gallons. They clip to the rim and pull water through a cartridge. They are straightforward to clean but the cartridges wear out and need replacing every few months, which adds cost.

Canister filters sit under the tank and pull water down through multiple stages of media. They cost more upfront but last longer and do not require cartridge replacements — you rinse the media instead. They are worth the extra money if you plan to keep the tank for years. Sponge filters are the cheapest option and work well for small tanks or breeding setups, but they are less efficient at removing waste and look less polished.

The filter's flow rate matters. It should turn over the tank's volume 4 to 10 times per hour. A 20-gallon tank needs a filter rated for 80 to 200 gallons per hour. Check the box before you buy — the number is always listed.

Heating, lighting, and water treatment

Most tropical fish need water between 75 and 80 degrees Fahrenheit. A submersible heater with a thermostat maintains this automatically. The wattage depends on tank size and room temperature — a 10-gallon tank in a cool room needs 50 watts, a 20-gallon needs 100 watts. Heaters cost $15 to $40. Without one, tropical fish become stressed and sick.

Lighting serves two purposes: it lets you see the fish and it drives the growth of live plants if you have them. A basic LED light strip costs $20 to $50 and runs 8 to 10 hours per day. Avoid leaving lights on 24 hours — fish need darkness to rest, and constant light causes algae problems.

Water treatment chemicals remove chlorine from tap water, which kills beneficial bacteria and harms fish. A bottle of dechlorinator costs $8 to $15 and lasts months. Some dechlorinators also bind heavy metals. If your tap water is very hard or very soft, you may need pH adjusters, but most tap water works fine without them. Test your water first before adding chemicals.

Substrate, plants, and decorations

Substrate is the material on the bottom of the tank. Gravel is the most common choice — it looks natural and lets beneficial bacteria colonize it. Sand is finer and better for fish that dig, like catfish, but it compacts and can trap waste. Bare bottom is easiest to clean but looks bare and gives bacteria less surface area to grow on. Plan on 1 to 2 pounds of substrate per gallon of tank volume.

Live plants are optional but helpful. They consume nitrate, which reduces algae, and they give fish places to hide. straightforward plants for beginners include Java fern, Anubias, and Amazon sword. They do not need special soil — they grow in regular gravel. Artificial plants work too and require no maintenance, but they do not reduce nitrate.

Decorations — rocks, driftwood, caves — give fish shelter and reduce stress. They also provide surface area for beneficial bacteria. Make sure anything you add is aquarium-safe. Rocks from outside can leach minerals or contain metals. Driftwood from pet stores is safe; driftwood from a river may not be. When in doubt, boil it first.

Setting up the tank step by step

Start by rinsing the tank with water only — no soap. Place the stand in its final location. Add substrate, rinse it first to remove dust. Fill the tank halfway with tap water, add dechlorinator, then add the heater and filter. Fill the rest of the way. Turn on the heater and filter and let them run for 24 hours before adding fish.

Test the water daily for the first two weeks. You will see ammonia spike first, then nitrite, then nitrate. When ammonia and nitrite are both zero and nitrate is present, the cycle is complete. This usually takes 4 to 8 weeks. If you add fish before this happens, do 25 percent water changes every other day to keep ammonia and nitrite low.

Once the cycle is complete, add fish slowly — no more than a few at a time, spaced a week apart. This lets the bacteria population grow to match the new bioload. Adding 10 fish at once will spike ammonia and kill them.

Ongoing maintenance and common problems

Weekly maintenance takes 30 minutes. Remove 25 percent of the water with a gravel vacuum, which sucks up waste from the substrate. Refill with treated tap water at the same temperature. Rinse the filter media in old tank water — tap water kills the bacteria. Check that the heater and filter are running and the temperature is correct.

Monthly, test the water. Ammonia and nitrite should always be zero. Nitrate should be below 40 parts per million. If nitrate is high, do larger water changes — 50 percent instead of 25 percent. If ammonia or nitrite appears, the tank is overstocked or the filter is failing.

Common problems include cloudy water (usually a bacterial bloom in the first week, harmless and temporary), algae blooms (too much light or too much waste), and fish dying for no obvious reason (usually ammonia or nitrite poisoning). A water test kit tells you which one it is. Never assume the fish are sick before testing the water.

Frequently Asked Questions

How long does it take before I can add fish?

The nitrogen cycle takes 4 to 8 weeks. You can add a few hardy fish after 2 weeks if you do frequent water changes, but waiting the full 8 weeks is safer. Some people use bacteria starter cultures to speed this up, but they are not reliable. The safest route is patience.

Can I use tap water straight from the faucet?

Tap water contains chlorine, which kills beneficial bacteria and harms fish. You must treat it with dechlorinator first. This costs a few dollars and takes seconds — just add the dose to the bucket before pouring it in. Some people let tap water sit for 24 hours to let chlorine evaporate, but dechlorinator is faster and more reliable.

What happens if I skip the water test kit?

You will not know if ammonia or nitrite is poisoning your fish until they are already dying. A test kit costs $20 to $30 and lasts for dozens of tests. It is the cheapest insurance you can buy. Without it, you are guessing, and guessing usually means dead fish.

Do I need a filter if I do water changes every day?

No, but daily water changes are exhausting and still less effective than a filter. A filter lets you do one 25 percent change per week instead. The filter also grows the bacteria that keep ammonia from spiking between changes. A filter is worth the money.

Can I keep the tank in my bedroom?

Yes, as long as it is not in direct sunlight and not near a heater or air conditioner vent. The filter makes some noise — usually a quiet hum, but some filters are louder. If you are a light sleeper, test the filter's noise level before you buy it, or choose a canister filter, which is quieter than a hang-on-back.