Goldfish Care And Breeding Guide (Husbandry, Spawning, Fry)
Goldfish (Carassius auratus) are hardy, cold-to-coolwater cyprinids available in two broad groups: single-tail (common, comet, shubunkin) and fancy, double-tail varieties (ryukin, oranda, ranchu, lionhead, black moor, telescope, pearlscale, veiltail, etc.). Single-tails are fast, streamlined swimmers that thrive in large tanks or ponds; fancy varieties are slower, more delicate, and better suited to spacious indoor aquariums with gentle flow.
Quick Facts
- Adult size: Single-tail 8-12+ in (20-30+ cm); Fancy 5-8 in (12-20 cm)
- Lifespan: 10-15 years typical; 20+ possible (esp. single-tails in ponds)
- Temperature: 65-74 degrees F (18-23 degrees C); Fancy toward the warmer end for stability
- pH / Hardness: pH 7.0-8.0; moderate hardness (GH -6-16 dGH)
- Behavior: Social, messy eaters; high oxygen demand and heavy bio-load
Tank Size, Filtration And Oxygenation
- Fancy goldfish: Start at 20 gal (75 L) for the first fish, add 10-20 gal each thereafter. Wide footprint tanks are best.
- Single-tail goldfish: Require very large aquariums (40-55+ gal for one juvenile) and are best long-term in ponds.
- Filtration: Aim for 8-10� tank volume per hour in turnover using canisters/HOBs plus a sponge filter for bio and fry safety.
- Oxygenation: Strong surface agitation and supplemental air stones are recommended.
- Water changes: 30-50% weekly (or more) to keep nitrate low and water stable.
Water Parameters
| Parameter | Target Range | Notes |
|---|---|---|
| Temperature | 65-74 degrees F (18-23 degrees C) | Keep stable; fancies prefer 70-74 degrees F. |
| pH | 7.0-8.0 | Stability > perfection; avoid sudden swings. |
| GH/KH | Moderate | Remineralize if using RO/DI; ensure buffering. |
| Ammonia/Nitrite | 0 ppm | Always zero; goldfish are sensitive. |
| Nitrate | Andlt; 20-40 ppm | Lower is better�achieve with heavy water changes And plants. |
Diet And Feeding
- Staple: High-quality sinking pellets or gel foods formulated for goldfish to reduce air gulping.
- Roughage And variety: Blanched leafy greens (spinach, lettuce), shelled peas, zucchini; plus frozen/live treats (daphnia, brine shrimp) for conditioning.
- Schedule: 1-2 modest meals/day for adults; juveniles may need 2-3 smaller meals. Avoid chronic overfeeding.
Aquascaping And Plants
- Substrate: Bare bottom or smooth sand/rounded gravel for easy cleaning.
- Hardscape: Avoid sharp decor; choose rounded wood/rock.
- Plants: Expect nibbling. Use hardy choices like Anubias and Java fern attached to wood/rock, fast growers (hornwort, Elodea/Anacharis), or artificial plants. Floating plants help nutrient export and shade.
Compatibility
Keep fancy goldfish with other fancies of similar speed. Avoid fin-nippers and tropical species that require warmer water. Single-tails are best with other single-tails (often outdoors). Many invertebrates and small fish will be eaten.
Common Health Issues
- Ich And external parasites: Quarantine new fish; treat promptly if white spots or flashing appear.
- Fin rot And ammonia burn: Prevent with strong filtration and large water changes.
- Buoyancy problems (fancies): Emphasize sinking foods, steady temperatures, and excellent water quality.
Breeding Goldfish (Overview)
- Maturity: Often 8-12 months; best results at 12-24 months.
- Seasonality: Spawning is triggered by �spring��gradual warming and longer light.
- Sexing: Males develop white breeding tubercles on gill covers/pectoral rays and chase females.
- Ratio: -2 males : 1 female improves fertilization and spreads chase stress.
Spawning Setup
- Condition breeders for 2-3 weeks with clean water and high-quality diet plus live/frozen foods.
- Use a 40-75+ gallon bare-bottom tub with a large sponge filter, vigorous aeration, and several spawning mops or brushes.
- Temperature: 68-72 degrees F (20-22 degrees C) for single-tail; 70-74 degrees F (21-23 degrees C) for fancies; gently manipulate by 2-3 degrees F to simulate spring.
- Once eggs are laid on mops, remove adults immediately (they will eat eggs).
Egg And Fry Care
- Incubation: -3-5 days at 72-75 degrees F (22-24 degrees C). Provide strong aeration across the mops.
- Antifungal (optional): Methylene blue ; remove opaque white eggs (infertile).
- First foods: After yolk sac absorption (24-48h post-hatch), feed infusoria/green water, then microworms and newly hatched brine shrimp 3-5� daily.
- Maintenance: Daily small water changes (10-20%), gentle flow, intense aeration, and size sorting to reduce bullying.
- Transition: Weeks 3-6 move to finely crushed pellets/gel foods; continue frequent changes for rapid growth.
- Culling ethics: Humanely rehome or cull severe deformities early; never release fish into the wild.
