How to Set Up Your First Aquarium: NZ Beginner's Guide

The quick answer: the single biggest mistake new fishkeepers make is buying fish the same day as the tank. A new aquarium has to be set up and cycled (grow its filter bacteria) for several weeks *before* fish go in, or the fish are likely to die. Get a tank that's bigger than you think you need, add the right gear, cycle it, and add fish slowly. Patience here is the whole game.

Choose the right tank

• Bigger is easier. A larger volume of water is far more stable and forgiving for beginners than a tiny bowl or nano tank. Aim for at least 50–60 litres to start. Avoid goldfish "bowls" entirely.
• Match fish to tank, not the other way around. Research the adult size and needs of any fish *before* you buy — goldfish, for example, get large and need much more room than people expect.

The gear you need

• Filter — the heart of the tank; it houses the good bacteria. See aquarium filter types in NZ.
• Heater (for tropical fish) with a thermometer.
• Substrate (gravel/sand), a light, and a lid.
• Dechlorinator/water conditioner — NZ tap water is treated with chlorine/chloramine which kills fish and filter bacteria; you must treat every drop you add.
• A liquid test kit (ammonia, nitrite, nitrate) — essential for cycling, not optional.

Set it up (step-by-step)

1. Rinse substrate and decor in plain water (never soap), place in the tank. 2. Add the heater and filter, fill with dechlorinated water. 3. Turn everything on and let it run. Set tropical heaters around 24–26°C (check your species). 4. Cycle the tank before any fish — this is the crucial bit, covered next.

Cycle BEFORE adding fish

A new filter has no bacteria to process the ammonia fish waste produces. You need to grow that bacteria first (the "nitrogen cycle"). This takes roughly 4–6 weeks and is the difference between fish that thrive and fish that die. Don't skip it — see how to cycle a new fish tank in NZ.

Adding fish

• Go slowly — a few hardy fish first, never a full tank at once.
• Acclimatise them to the temperature by floating the bag, then mixing in tank water over 20–30 minutes before releasing.
• Don't overfeed — see how often to feed fish in NZ.

Quick takeaways

• Never buy fish and tank the same day — cycle first (4–6 weeks).
• Bigger tanks are more stable; skip bowls and nano tanks as a beginner.
• Must-haves: filter, heater (tropical), dechlorinator, liquid test kit.
• Always treat NZ tap water for chlorine before it touches the tank.
• Add fish slowly and acclimatise them to temperature.

Shop related categories at PetMall

Looking for tanks, filters, heaters and water conditioner in New Zealand? Browse the PetMall fish range for current options and nationwide delivery.

-> Browse Fish & Aquarium Supplies

Related reading

• How to Cycle a New Fish Tank NZ
• Aquarium Filter Types NZ
• How Often to Feed Fish NZ

References

• NIWA / NZ water treatment (chlorine in tap water), general guidance, checked 2026-06-05: https://www.water.org.nz/
• SPCA New Zealand, fish welfare, checked 2026-06-05: https://www.spca.nz/advice-and-welfare/

Important notice

*General fishkeeping information for NZ owners. Species needs vary — research each fish's adult size and water requirements before buying.*