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Learn Aquarium Keeping

Set up a stable tank, cycle it properly and keep fish that thrive for years.

Free to start. Built from a single prompt. No credit card.

Aquarium keeping is really water keeping. Fish produce ammonia, and a healthy tank relies on colonies of beneficial bacteria in the filter that convert it to nitrite and then to less harmful nitrate, which you remove with water changes. Understanding that nitrogen cycle, and waiting for it to establish before adding fish, prevents most beginner losses. From there the hobby opens into planted tanks, aquascaping and breeding. Learnr builds a personalized course of short lessons on equipment, cycling, water testing, stocking and maintenance, for freshwater tanks and, later, saltwater.

How to learn Aquarium Keeping, step by step

Choose a tank big enough to be stable. Larger volumes of water change temperature and chemistry more slowly, so a modest tank of around 20 gallons is often easier than a tiny one. Add a filter rated for the volume, a heater for tropical fish and a lid.
Cycle the tank before adding fish. Add an ammonia source to an empty, filtered tank and test until ammonia and nitrite drop to zero within a day and nitrate appears. Fishless cycling commonly takes several weeks. Bottled bacteria can help, but testing confirms the result.
Get a liquid test kit and use it. Test ammonia, nitrite, nitrate and pH, and know what your tap water reads too. Always treat tap water with a dechlorinator that also neutralizes chloramine before it goes into the tank.
Research every species before buying. Check adult size, temperament, preferred water and whether the fish needs a group. Plenty of fish sold small grow too large for home tanks. Learnr lessons let you compare species and build a compatible stocking plan.
Stock slowly and quarantine. Add a few fish at a time and give the bacteria a week or two to catch up, testing as you go. Ideally keep new arrivals in a separate quarantine tank for a few weeks to avoid spreading disease.
Keep a steady maintenance routine. Change a portion of water regularly with temperature-matched, dechlorinated water, vacuum debris from the substrate and rinse filter media in old tank water rather than tap water, so you do not kill the bacteria.

What you'll learn

Explain the nitrogen cycle and cycle a new tank before adding fish
Test and interpret ammonia, nitrite, nitrate and pH
Choose fish that suit your tank size and each other
Run a maintenance routine of water changes and filter care
Set up and maintain a simple planted aquarium

What's inside your Aquarium Keeping course

A sample path Learnr builds for Aquarium Keeping. Your real course adapts to your goal and level.

1. Tank size, filter, heater and lighting
2. The nitrogen cycle and fishless cycling
3. Water testing and parameters
4. Choosing and stocking fish
5. Maintenance and water changes
6. Plants, aquascaping and common diseases

How long does it take to learn Aquarium Keeping?

Setup and cycling take several weeks, and that waiting is part of learning. Most people feel comfortable with a community freshwater tank after a few months. Planted tanks and saltwater reefs involve much more chemistry and can take a year or more to master.

What you need before you start

No experience needed. You need space for a tank on a sturdy surface near an outlet, a budget for equipment and patience to cycle the tank before buying fish.

Common mistakes to avoid

Adding fish the day the tank is set up, which exposes them to ammonia spikes. Cycle the tank first and confirm with tests.
Cleaning the filter under tap water, which kills beneficial bacteria. Rinse filter media gently in removed tank water.
Buying fish on impulse that grow too large or fight tankmates. Research adult size and compatibility first.

How Learnr builds your course

Type your topic

Tell Learnr you want to learn Aquarium Keeping, or get as specific as you like.

Get a personalized course

Learnr instantly builds a full Aquarium Keeping course tailored to your goal and skill level.

Learn and level up

Move through bite-sized lessons and interactive practice, earning XP and keeping your streak.

Aquarium Keeping questions, answered

What is the easiest fish for beginners?

Hardy, peaceful species suited to your water, such as many small tetras, corydoras or livebearers, are common starting choices. The right answer depends on your tank size and local water, so research before buying.

Can goldfish live in a bowl?

Goldfish produce a lot of waste and grow much larger than many people expect, so they do poorly in small bowls. They need a large, well-filtered tank or a pond.

What should I do with fish I can no longer keep?

Rehome them through a local fish store, club or other hobbyists. Never release aquarium fish or plants into the wild, which can harm native ecosystems and is illegal in many places.