Goldfish tank: step-by-step setup

4 steps from choosing the spot to adding the first fish.

1. 75 L + 40 L each

   Goldfish are messy and grow 15–20 cm: no bowls. Filter at 8–10×, no heater (18–24 °C). Keep fancies apart from fast single-tails.

2. Cycle the tank (the key step)

   Fill with dechlorinated water, run filter and heater, add an ammonia source (a pinch of food daily or 2 ppm ammonia) plus bottled bacteria. Test every two days: ammonia rises, then nitrite, then nitrate. Ready when ammonia and nitrite read zero three times in a row and nitrate shows (2–6 weeks). Log the tests and Zajel shows the stage.

3. Feeding

   Sinking pellets (gulping air causes swim-bladder trouble) and shelled peas weekly.

4. Bigger changes

   30–50% weekly; nitrate under 40.