圆尾斗鱼 · Roundtail Paradise Fish

Overview

The round-tailed labyrinth fish Macropodus ocellatus is adapted to seasonal temperature changes. Males become territorial during reproduction. Many suitable indoor setups need no continuous heating, and a cool winter interval may be beneficial.

Distribution & habitat

It has a broad range across China, Korea, and Japan, extending on the Chinese mainland from the Pearl basin to the Amur. Northeastern Vietnam is a possible additional locality; Russian Amur populations may be introduced. Zhoushan is the type locality.

Habitats include irrigation ditches, rice fields, pools, marshes, streams, and river backwaters. Northern sites can freeze at the surface in winter, illustrating strong seasonal adaptation.

Aquarium setup

A pair requires a footprint of at least approximately 80 × 30 cm. Roots and branches provide shade, with floating or surface plants important for nest building. Leaves add shelter and microorganisms useful to newly feeding fry. Fully furnished or easily maintained bare-bottom layouts are both possible.

In suitable indoor conditions, heating is often unnecessary. Evidence suggests a winter cooling period can benefit the fish.

Diet & feeding

Insect larvae and similar small animals are likely natural prey. Offer small live or frozen Daphnia, Artemia, and worms. Some quality dry products may also be accepted.

Behaviour & compatibility

Reproductive males defend territories actively. Groups are possible in sufficiently spacious aquaria with plentiful structure, but the minimum pair accommodation should not be treated as a group tank.

Sexual dimorphism

Males grow larger and develop extended soft rays in the dorsal, anal, and caudal fins.

Breeding

The male constructs a bubble nest among surface plants and generally tolerates females nearby during construction, so prior separation is unnecessary. Soft water and a modest temperature increase are reported spawning stimuli. A close-fitting cover retains warm, humid air for developing fry.

Once the nest is ready, fin displays lead to embraces beneath it. Eggs contain an oil droplet and float upward, often assisted by the male. Repeated batches typically produce several hundred eggs.

Adults can initially remain, with shelter for the female. The nest may break apart and the eggs become gathered into a cluster. Hatching takes around 3–4 days, after which larvae stay until yolk absorption. Remove adults when free swimming begins and male care wanes.

For the first few days, provide infusoria-sized food, then introduce microworms and Artemia nauplii. Use small, regular water changes.

Notes

Older accounts may use Macropodus chinensis, a name now treated as a synonym of M. opercularis, making historical identification confusing. A rounded tail and an eye stripe disconnected from the gill-cover spot help identify this species.