13/06/2026
One of the biggest winter mistakes in fishkeeping? Using a heater that’s too small 🐠❄️
It might still turn on… but that doesn’t mean it’s doing enough.
Here’s what happens when a heater is undersized:
• it struggles to hold temperature in colder rooms
• water slowly dips below ideal range overnight
• fish get repeated stress cycles (warm → cold → warm again)
And fish don’t adapt well to that kind of fluctuation - it weakens their immune system over time.
A properly sized heater does something different:
✔ holds temperature steady
✔ doesn’t have to “fight” the cold constantly
✔ creates a stable environment your fish can rely on
👉 If your tank takes ages to warm up in the morning, that’s usually a sign your heater is working too hard (or not hard enough).
Need help choosing the right size? We can match it to your setup or shop our heaters here - aquarays.co.nz/?s=heater
