Cualac tessellatus · Checkered Pupfish

Overview

An uncommon Mexican spring pupfish, Cualac tessellatus has especially demanding water requirements for successful egg development. Adults may survive conditions that do not support reproduction, so simple survival is not evidence that a breeding colony is secure.

Distribution & habitat

It is confined to a few springs in the Río Verde valley of San Luis Potosí, including Media Luna and nearby lagoons. Gypsum-rich geology supplies very hard groundwater, with thermal springs at some sites.

Fish mainly use shallow pool margins and natural channels over mud and detritus, among lilies, filamentous algae, and occasional wood. Conditions vary among springs, and water diversion, recreation, aquaculture, and introduced fishes have affected these restricted habitats.

Aquarium setup

A pair can use the minimum suggested aquarium, while groups benefit from a larger tank or container. Plants and spawning mops break sightlines and provide refuge. Air-powered sponge filtration reduces risks to eggs and fry. Lighting is flexible, but filamentous algae are worth encouraging.

Very hard water is crucial for reproduction because soft conditions impair egg development. Slowly dissolving pure gypsum pieces have produced particularly good results.

Diet & feeding

Small crustaceans, worms, insect larvae, and other tiny animals dominate its natural feeding, with algae and plant material also consumed. Most fish accept dry foods, supplemented regularly with live or frozen Artemia, Daphnia, or bloodworms. Include a quality plant- or algae-based preparation if filamentous algae are absent.

Behaviour & compatibility

A dedicated breeding group is preferable, although compatible hard-water companions are possible. Groups generally coexist well. Breeding males establish temporary territories, with disputes apparently consisting mainly of chasing rather than biting.

Sexual dimorphism

Males have strong variable vermiculated flank markings, yellow-orange pelvic and anal fins, a bluish speckled dorsal, and a dark tail. Females are plainer, with weaker flank markings and limited dark dorsal pigmentation.

Breeding

With appropriate mineral conditions, captive reproduction is achievable. Warm conditions allow frequent batches, though a spring and late-summer seasonal pattern is preferable. Males defend temporary sites and court females; single eggs or small batches attach to algae and other surfaces by threads.

Some eggs may be eaten, yet covered group tanks can produce surviving fry. For higher yields, move eggs to separate water matching adult chemistry and temperature. Incubation usually lasts 7–14 days, and newly swimming fry accept Artemia nauplii and microworms.