Telescope Goldfish
Carassius auratus
Cyprinidae
FishDifficulty: ●●●●○Data: well-established
About
The telescope, known in Japan as the demekin, is a fancy goldfish bred for eyes that protrude from the sides of the head. In body it is essentially a ryukin — short, round and twin-tailed — and it reaches about 20 cm of body length with the fins on top of that, so it is no small-tank fish. Despite those eyes its sight is poor: it finds food slowly, gets outcompeted by quicker tankmates, and damages its eyes easily on sharp rock or decor. The black moor is the same breed in black.
Care
Three adults need a base of at least 120 x 60 cm; a single fish needs 150 L and a 110 cm tank. Keep flow gentle, use small rounded gravel and nothing sharp, feed sinking pellets and give it time to find them. Do not mix it with active single-tail goldfish.
Diet
Omnivore that must be fed slowly and deliberately, because poor vision means it eats last. Small portions of pre-soaked sinking pellets twice daily, plus frozen bloodworm and daphnia.
Tankmate compatibility
Possible with care (38)
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Avoid (233)
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Computed by the AquaSage engine for a spacious reference tank — always check the full verdict for your exact setup in the calculator.
Telling males from females
What works for this species, most reliable first.
- Breeding tuberclesStrong · only in breeding condition — they vanish out of season
Goldfish and their cyprinid relatives grow small white bumps on the gill covers and leading pectoral rays when they come into breeding condition.
Frequently asked questions
- What tank size does a Telescope Goldfish need?
- A Telescope Goldfish needs an aquarium of at least 150 litres (39.6 US gallons) with a footprint at least 110 cm (43.3 in) long — for this species, swimming length matters as much as raw volume.
- What water parameters does a Telescope Goldfish need?
- Telescope Goldfish does best at 10–25 °C (50–77 °F), pH 6–8 and a general hardness of 6–25 °dGH.
- What group size does a Telescope Goldfish need?
- Telescope Goldfish is a social species — keep a group of at least 2 so natural behaviour emerges and stress stays low.
- Is the Telescope Goldfish suitable for beginners?
- Telescope Goldfish is a demanding species best attempted with some experience — it needs stable, closely watched conditions to thrive.
Sources
Water & tank
Temperature10–25°C
Optimal temp.16–21°C
pH6–8
Hardness (GH)6–25°d
Carbonate (KH)4–15°d
Adult size20 cm
Min. volume≥ 150 L
Min. tank length≥ 110 cm
Group size≥ 2
Swimming zoneAll levels
TemperamentPeaceful
Water typeFreshwater
FlowLow
Lifespan~12 yrs
Try in the calculator