Before your first fish
The tank isn't ready
when it looks ready.
It's ready when the water tests clean — and that takes weeks of growing bacteria you will never see. Almost every dead first fish traces back to this one step.
- NH₃ AmmoniaBurns gills
- NO₂⁻ NitriteStarves blood of oxygen
- NO₃⁻ NitrateYou remove this by hand
The whole job, start to finish
Five steps, in the order they matter
Most first tanks fail at step three, because it is the only one you cannot see happening. Work through these in sequence and yours won't.
- 01
Choose a tank
Bigger is easier. Settle the size before you buy anything else.
Day 1 - 02
Buy the right gear
Filter, heater, light, substrate, test kit. The rest can wait.
Day 1 - 03
Cycle it
Grow the bacteria, with no fish in the tank. This is the step people skip.
Weeks 1–6 - 04
Add your first fish
Slowly, and fewer than the shop suggests. Temperament matters as much as size.
Week 6+ - 05
Keep a routine
A weekly water change and a monthly filter check is most of the job.
Weekly
Keep this handy
What a healthy tank reads
Test weekly for the first two months. Numbers, not the look of the water, tell you whether anything is wrong.
- Ammonia
- 0ppmAnything above zero is an emergency
- Nitrite
- 0ppmAlso an emergency. No safe level
- Nitrate
- < 40ppmWater changes bring this down
- Temperature
- 24–26°C75–79°F for most community fish
- pH
- 6.8–7.6Stable matters far more than exact
Browse by subject
Everything you'll need to look up
Start here
Choosing a first tank and size, what a setup really costs, and where to put it.
ReadEquipment
Filters, heaters, lighting and substrate — what matters, and what you can skip.
ReadWater & cycling
The nitrogen cycle, fishless cycling step by step, and the numbers to test for.
ReadFish & plants
Beginner-friendly species, honest stocking limits, and plants that live without CO₂.
ReadLatest guides
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