Aquarium fish breeding fundamentals
Livebearers, egg-layers, separate spawning tank — what you need to know before your first breeding attempt.
Breeding is the natural extension of the hobby. The first batch of fry turns an aquarium from a 'display' into a living ecosystem. But not every species spawns easily, and without preparation 90 % of fry die.
Two reproductive modes
Livebearers (guppies, platies, mollies, endlers) — females release fully formed fry that the parents themselves eat. Egg-layers (tetras, angels, cichlids, barbs) — scatter eggs and need a dedicated spawning tank.
Where to start
Easiest: guppies and platies. Females will drop fry without intervention 4–6 weeks after purchase. Medium: angelfish (the pair tends the eggs). Hardest: discus and many tetras (RO water, soft, acidic).
Spawning tank
20–30 L with a sponge filter (won't suck in fry), dense plants or a spawning net, warm water. When the female is ready — move the pair to the spawning tank; after spawning, return parents to the main tank (or they will eat the eggs).
Triggering spawning
• 30 % water change with cooler water mimics the rainy season. • Heavy feeding of bloodworm and brine shrimp for 2 weeks. • Drop pH by 0.5 (catappa leaves, peat) — for Amazonian species. • Long photoperiod 12–14 hours.
Raising fry
Micro-food: infusoria for the first 3–5 days, then brine shrimp nauplii (hatch in 24–36 h), specialized fry flakes. Feed 4–6 times daily in tiny portions.
Water changes and cleanliness
Fry are sensitive to ammonia. Change 10–15 % every 2–3 days, siphon food leftovers daily. Without fanaticism though — stress kills fry just as easily.
When to sell
Guppy fry sell from 8–10 weeks (3–4 cm), tetras from 3–4 months. Pet shops usually pay 30–50 % retail but take the whole batch.
First fry are the most magical feeling in aquaria. Every hobbyist owes themselves the experience at least once.
FAQ
- Can I breed without a dedicated tank?
- Only livebearers in heavily planted setups (some fry survive in floating plants). For egg-layers a spawning tank is mandatory — parents eat the eggs 99% of the time.
- How many fry from one female guppy?
- 20–50 per drop every 4–6 weeks. One female yields 200–400 fry per year, of which 30–50% survive. Plan for overcrowding or selling.
Goldie editorial team
Practising aquarists with a combined 30+ years of experience · Biologists and editors, fact-checking against FishBase and Seriously Fish · Every piece is reviewed by a qualified ichthyologist before publication
Veterinary ichthyologist, specialist in aquarium fish diseases
DVM in veterinary medicine, University of Milan · PhD in hydrobiology, specialising in ornamental fish diseases · 10+ years of private veterinary practice with aquatic species
Sources
- Seriously Fish — breeding guide overview · Seriously Fish · 2026-05-29
- Practical Fishkeeping — breeding articles · Practical Fishkeeping · 2026-05-29