Guppy fry can grow surprisingly fast, but most “slow growth” problems are really water quality problems. Fry are tiny, they eat often, and leftover food turns into waste quickly. The goal is simple: feed enough for steady growth, while keeping ammonia and nitrite at 0.
The best grow-out setup (low drama)
- Tank size: 20–60L depending on how many fry you’re raising.
- Filter: a sponge filter is ideal. It’s fry-safe, gentle, and easy to clean.
- Temperature: 24–26°C for consistent appetite and growth.
- Cover: a small plant clump or spawning mop helps fry feel secure.
Feeding rhythm that works
Instead of big meals, fry do better with small meals more often. A realistic routine:
- 2–3 feeds/day: powdered fry food or finely crushed flake.
- 1 feed/day (optional): baby brine shrimp or daphnia for growth and conditioning.
Feed only what disappears quickly. If food collects on the bottom, siphon it out and reduce the next feed.
Water changes: the growth “secret”
Clean water is what lets fry convert food into growth instead of stress. For grow-out tanks, aim for:
- 20–30% twice per week for moderate stocking
- 20% every other day if you’re raising a heavy batch
Always dechlorinate and match temperature. Sudden swings stunt growth and cause clamping.
Sort by size (avoid runts)
Once fry start showing a size spread, the biggest ones will outcompete the smaller ones at every feed. If you can, split them into two groups (larger and smaller). This single step usually fixes “mystery runts” and improves overall uniformity.
Signs your routine is working
- fry are active and pecking constantly
- bellies look gently rounded after feeding (not bloated)
- water stays clear and ammonia/nitrite stay at 0
Fast growth is not about pushing huge meals — it’s about steady food plus clean water. If you keep that balance, fry develop stronger bodies and better finnage, and you’ll have healthier juveniles to select from later.
