Where to start
Aquarium beginner guide: how to set up your first fish tank, step by step
The complete new aquarium setup, from choosing the tank to the first fish, in the right order.
Setup & stockingBest fish for a 10 gallon tank: species, numbers and stocking ideas
The most popular starter size: species, numbers and five ready-to-copy stocking plans.
Setup & stockingBest fish for a 5 gallon tank: what really fits and how many
What really fits in 5 gallons: a betta, a tiny school or a shrimp tank, and what to avoid.
Setup & stockingBest fish for a 20 gallon tank: stocking ideas that actually work
Enough room for a true community with a school, a bottom group and a centerpiece.
Setup & stockingPeaceful community fish: the best non-aggressive species to keep together
Calm species that live together without nipping, chasing or eating each other.
Setup & stockingBest fish for a 55 gallon tank: stocking plans for a real community
Stocking ideas for a large tank, from big schools to angelfish and gouramis.
01
What this aquarium setup guide covers
Setting up a tank is two jobs: building a stable environment, then choosing fish that fit it. This section covers both. Start with our step-by-step beginner aquarium guide for the build itself, then use the stocking pages to match fish to your tank size and water.
02
New aquarium setup in 8 steps
Whatever the size, a new aquarium setup follows the same order. Skipping the cycle is the mistake that costs the most fish.
- Choose the tank: 10 to 20 gallons is the easiest size for a first aquarium
- Place it on a level stand rated for the full weight, about 10 lb per gallon once filled, away from windows and radiators
- Rinse and add substrate, then hardscape (rocks, wood)
- Plant, then fill slowly with water treated with a conditioner
- Install and start the filter, heater and thermometer
- Cycle the tank until ammonia and nitrite stay at zero
- Add the first small group of fish, acclimated gently
- Build up stocking over several weeks while testing the water
03
Choosing a tank size
Bigger is easier. More water dilutes mistakes and keeps temperature steady, which is why most keepers recommend 10 gallons as the minimum for a beginner and 20 gallons as the comfortable choice. A 5 gallon tank works well for a single betta or a shrimp colony, but it leaves little margin. Compare complete kits in our guides to the best 10 gallon aquarium, the best 20 gallon aquarium and the best 55 gallon aquarium.
04
Stocking by tank size
Once you know your volume, pick the matching list: fish for a 5 gallon tank, the best fish for a 10 gallon tank, the best fish for a 20 gallon tank and the best fish for a 55 gallon tank. Each gives species compared side by side, numbers, sample communities and fish to avoid.
If you are unsure about compatibility, start from our list of peaceful community fish or our tank mates guides, which cover popular centerpiece fish one by one.
05
Equipment you need from day one
A tropical freshwater tank needs four things running before fish arrive: a filter sized for the tank, an adjustable heater, a light and a water conditioner. Our aquarium filter reviews and aquarium heater reviews explain what size to buy, and a liquid test kit tells you when the tank is ready.
Every guide in this section
- 01Best fish for a 5 gallon tank: what really fits and how many
- 02Best fish for a 10 gallon tank: species, numbers and stocking ideas
- 03Best fish for a 20 gallon tank: stocking ideas that actually work
- 04Best fish for a 55 gallon tank: stocking plans for a real community
- 05Peaceful community fish: the best non-aggressive species to keep together
- 06Best fish for small tanks: 14 nano fish and invertebrates that actually fit
- 07Aquarium beginner guide: how to set up your first fish tank, step by step
Frequently asked questions
Frequently asked questions
How long does it take to set up an aquarium?
The physical setup takes an afternoon, but the tank is not ready for fish until it is cycled, which usually takes 4 to 8 weeks. During that time beneficial bacteria grow in the filter and convert ammonia into nitrate. Bottled bacteria and seeded filter media from a healthy tank can shorten the process.
What size aquarium is best for a beginner?
A 10 to 20 gallon tank. It is small enough to maintain easily and fits most rooms, yet large enough that temperature and water quality stay stable. Very small tanks under 5 gallons look simple but react to every mistake, which makes them harder for beginners.
Can I add fish the same day I set up my aquarium?
No. A new tank has no bacteria to process fish waste, so ammonia builds up quickly and can kill fish within days. Cycle the tank first, or if you must do a fish-in cycle, add only a few hardy fish and test the water daily, changing water whenever ammonia or nitrite appear.
How many fish should I add at first?
Add a small group, about a quarter to a third of the planned stocking, then wait two to three weeks and test the water before adding more. This gives the bacteria time to grow with the waste load. Start with the hardiest species and add sensitive fish last.
Written and reviewed by the handsoffmyhobby editorial team according to our editorial policy.
