Ideal Parameter Range
pH: 7.0-8.0 (slightly alkaline preferred). GH: 8-12 dGH (moderately hard). KH: 6-10 dKH (stable buffer). Temperature: 75-80°F.
Guppies tolerate pH 6.5-8.5 but break down outside that range. Soft water (GH below 5) causes fry mortality and color loss within months.
Adjusting Soft Water
If your tap water is soft (common in rainy regions, well water, or RO systems), add Seachem Equilibrium or crushed coral substrate to raise GH. A small mesh bag of crushed coral in the filter works well as a slow buffer.
Aragonite sand substrate also slowly dissolves and maintains hardness. This is the easy long-term solution for soft-water areas.
- ✦Test GH and KH monthly — they drift over time.
- ✦Stable parameters matter more than perfect ones.
Why Hard Water Matters
Guppies use calcium and magnesium for scale, fin, and skeletal development. In soft water, fry develop deformities (curved spines, missing fins) and adults lose color intensity.
Hard water also stabilizes pH — KH acts as a buffer. Soft-water tanks crash pH overnight, killing fish suddenly.
Temperature Effects
Higher temperatures (80°F) speed metabolism — faster growth, more frequent breeding, but shorter lifespan. Lower temperatures (74°F) slow everything but extend life.
For best balance: 78°F. For breeding programs: 80°F. For longevity: 75°F.