Guppies prefer stable, mineral-rich water. In Australia, many tap water supplies are already in a workable range. The key is not chasing “perfect numbers” — it’s keeping parameters consistent so fish don’t experience sudden swings.
Targets that work for most guppy tanks
- Temperature: 24–26°C (stable appetite and colour; consistent breeding).
- pH: 7.0–7.8 (stability beats precision).
- GH (hardness): ~8–14 dGH (supports colour, fertility, fry development).
- KH (buffer): ~3–6 dKH (prevents pH swings between water changes).
Why KH matters more than most people think
KH acts like a shock absorber for pH. If KH is very low, pH can swing after feeding, during cycling, or between water changes. Guppies often show stress (clamped fins, poor appetite) from swings even when “average pH” looks fine.
How to adjust gently (avoid sudden shifts)
- Raise KH: a small bag of crushed coral in the filter adds buffering gradually over days.
- Raise GH: measured remineralisation salts can help in very soft-water areas.
- Lower pH safely: more plants, consistent small changes, and driftwood can nudge pH down slowly. Don’t force big drops with chemicals.
Testing that actually helps
For day-to-day care, ammonia and nitrite matter most (both should be 0). Nitrate is your “long-term load” indicator; many keepers aim to keep it under ~30 ppm. If nitrate rises quickly, reduce feeding slightly and increase consistency of water changes.
One habit that prevents most issues
Always match temperature and dechlorinate new water before changes. Many guppy “mystery problems” start right after a poorly matched water change.
If you want a quick check of your local readings, you can send your GH/KH/pH numbers and we’ll suggest gentle tweaks that keep your tank stable without chasing perfection.
