Lesson 4: Caring for Fry (Baby Guppies)

Raising Baby Guppies

Guppy fry are born fully formed and ready to swim, but they're incredibly tiny — about 6-7mm long. They're also on the menu for every adult fish in the tank, including their own mother. Here's how to help them survive and grow.

The First 24 Hours

• Newborn fry will immediately swim to the surface and seek cover
• They're born with a tiny yolk sac that sustains them briefly
• You can start offering food within a few hours of birth
• Don't panic if they hide — hiding is survival instinct and a good sign

Feeding Fry

Baby guppies need to eat 3-4 times daily in very small amounts. Their options:

• Crushed flakes — Grind regular flakes into a fine powder between your fingers. The particles should be tiny.
• Baby brine shrimp — The gold standard for fry food. You can hatch them yourself with a simple kit. Highly nutritious and fry go crazy for them.
• Commercial fry food — Products like Hikari First Bites are designed for newborn fish.
• Micro worms — Easy to culture at home and excellent nutrition.

⚠️ Important: Remove any uneaten food after a few minutes. Fry tanks get dirty fast with frequent feedings.

Fry in the Main Tank

If you're letting fry grow up in the main tank with adults:

• Dense plants are essential — Java moss, water wisteria, and floating plants provide life-saving cover
• Expect natural losses — Some fry will be eaten. This is normal. The ones that survive tend to be the quickest and healthiest.
• Feed a little extra (carefully) so fry get a chance to eat before adults consume everything
• Fry that survive the first 2 weeks are usually home free

Fry in a Nursery Tank

If you've separated them:

• Keep the water warm (78-80°F)
• Use a sponge filter only (no HOB filters that could suck them up)
• Do small, frequent water changes (10-15% every 2-3 days)
• Match the water temperature when doing changes — fry are sensitive to sudden shifts
• Keep the light on a normal schedule

Growth Timeline

• Week 1-2: Tiny, mostly hiding, eating crushed food
• Week 3-4: Noticeably bigger, more confident, starting to show faint color
• Week 6-8: You can start seeing male vs. female differences
• Week 8-12: Colors develop, personalities emerge
• Month 3-4: Approaching adult size, can be safely added to the main tank

When to Move Fry to the Main Tank

The general rule: when they're too big to fit in an adult's mouth. This is usually around 1-1.5cm long, or about 4-6 weeks old. By then, they can hold their own.

What I Wish I'd Known

You don't need to save every single fry. I know that sounds harsh, but trying to raise 50+ babies from every batch is unsustainable. Let nature take its course in the main tank, and selectively raise the ones you're most excited about. Quality of care over quantity.

Next up: Lesson 5 — Managing Population