In the Freshwater Aquarium Again Quiz

Answer: the Green Tiger Barb.

Aquarium strains of both Platies and Swordtails are hybrids among several Mexican Xiphophorus species, and will even hybridize with one another. "Sunset" Gouramis are not selections of one species, but hybrids between two Colisa species. Green Tiger Barbs, however, are "melanistic" mutations of the species Puntius tetrazonus.

Their genes merely code for some extra black coloring, which gives them their green iridescence.

Answer: carbon dioxide.

The carbonate in the gravel reacts with the acid of vinegar to produce bubbles of carbon dioxide. By a similar reaction of carbonate and (citric) acid, CO2 fizzes in your Alka-Seltzer! Carbonates would slowly dissolve out of this gravel and raise alkalinity and the pH in your aquarium, if you used it. (Hydrogen sulfide is produced quite differently, by anaerobic bacteria in pockets of very low oxygen.)

Answer: Yes

Yes. Many Corydoras species spawn at the onset of the rainy season, when temperatures quickly drop in a spate of cool rainwater runoff. The temperature drop won't harm them at all. Some breeders even wait for the barometric pressure to fall, too.

Answer: mouthbrooding.

Though mouth-brooding behavior to protect the eggs from marauders has developed in other groups of fishes, such as Bettas, a majority of the world's mouth-brooding fishes are concentrated among the cichlids of Lake Malawi.

Answer: they're bound together in a gelatinous mass.

Fish eggs or snail eggs may be a clear golden color, and you may detect the dark developing snail or the eyes of the larval fry within each egg, but unlike fish eggs, snail eggs are deposited in a mass that's encased in jelly.

Answer: True

True. They display only enough aggression to preserve a minimal space between individuals, and males and females are virtually identical, until females swell with eggs at spawning season.

Answer: true

The Texas Cichlid originally was restricted to the lower Rio Grande basin. Other cichlids found in U.S. waters, like the Florida sportsman's "Peacock Bass," are exotic escapees.

Answer: lush Amazon Swordplants.

The dim halflight under an unbroken tree canopy discourages plant growth in rainforest watercourses. Tree leaves and woody debris are more common in the dark waters that are stained with tannins and other humic acids.

Answer: True

Yes, they are rendered into harmless chlorides. With chloramines, the sodium thiosulfate does release some free ammonia, however, and that may be a cause for concern.

Answer: perceiving sound.

The fishes' swim bladder resonates to vibrations like the woofer of a speaker. These small bones link the swim bladder and the inner ear, enabling Carp, Characins and Catfishes and others to hear higher frequency sounds.