If you are looking for something a little out of the ordinary you may like to consider the leaf fishes. These members of the family Nandidae occur in South America, Africa, and Asia.
If you have read through the catfishes chapter you will already be aware of Malapterurus electricus (Electric catfish). There are, however, several other fishes that are able to produce electricity.
The characins are a large group of freshwater fishes found in South and Central America and Africa. They are characterized by the Weberian Apparatus (the linkage of bones between the swimbladder and the inner ear) that allows them to hear high frequency sounds.
These plants are more decorative than functional. However, when planted in containers on the marginal shelf—the ledge around the inside of preformed ponds, about 12 in (30 cm) below the surface—they can provide retreats for young fish. Marginals can also be grown as edging plants, giving the pond a more informal look and creating a barrier that makes it more difficult for predators to reach the fish. Some marginals trail down into the water, which helps to hide the perimeter from view. All the plants featured here are suitable for temperate climates, but some will benefit from protection in winter.
These plants are not renowned for their flowers, but they give the pond a more natural feel and are important for the well-being of the fish. They spread to form a dense mass, protecting the fish from predators, especially birds, and also from sunburn, in addition to curbing algal growth. Furthermore, they provide spawning sites and food for some species of fish. Floating plants are easy to establish—simply let them drift on the surface until they find a suitable position—and they develop much faster in a new pond than other types of plants, such as marginals and water lilies. Some popular varieties originate from warm climates and are not hardy in temperate areas. They should be brought inside to protect them from winter frosts.
Sea horses are among the most instantly recognizable and fascinating of all marine fish. Less well known, however, are their elongated relatives called pipefish.
A number of marine fish from other diverse groups are occasionally available to aquarists. Their requirements differ widely; some predatory species need a fish-only setup, while others can be housed safely in a reef aquarium. Never be tempted to choose a fish simply by its appearance.
There are few more diverse invertebrate groups than the mollusks. Marine gastropod mollusks possess a protective shell and a “foot” for locomotion, just like the land snails.
Closely related to the triggerfish, filefish are not so boisterous in aquarium surroundings as their cousins, nor as destructive. Most species are smaller than triggers, but they share with them the split configuration of the dorsal fin (the first part forms a spine used to anchor the fish in a cave). The ventral fin on the underside of the body is similarly modified, providing additional support.
