I have set up tanks that crashed in week two and tanks that are still stable years later. The difference is almost never luck. This guide walks the 15-gallon setup from empty glass to stable, livable water without the usual week-two crash.
What you need
- A 15-gallon tank and a stand rated for the weight (~60 kg when full).
- Filter rated for at least 60 L/h.
- Heater (if tropical): 126 W.
- Substrate: 5 cm deep.
- Live plants and a light on a 7-hour timer.
Step by step
- Rinse substrate, add it, and hardscape before filling.
- Fill slowly to avoid clouding; start the filter and heater.
- Cycle the tank — see our lowering nitrates guide guide guide — for 21 days until ammonia and nitrite read 0 ppm.
- Test water, then add a small group of hardy fish; build up slowly.
Common mistakes
Adding fish during the first week, skipping the cycle, and skipping water tests are the big three. A 21% water change weekly, using our constipation in fish: bloating and the pea fix guide, prevents most problems before they start.
Next steps
Once stable, layer in more plants and a few peaceful tank mates. Keep a log of parameters; a tank you measure is a tank you can trust.
Spending smart
You can build a solid 15-gallon tank without premium gear: a reliable filter, a second-hand stand, and easy plants do most of the work. Spend on the heater and test kit, where cheaping out costs fish.
