What to look for when buying fish.
Features of acquiring Perciforms.
• Indian glassy fish (Chanda ranga) and Wolf’s glassfish (Chanda wolffii). These fish are considered difficult to keep, and keeping them in a community aquarium is undesirable – set up a separate one for them. Glass fish are often sold with a fluorescent dye injected into their bodies and passed off to inexperienced hobbyists as glowing fish. The fish have simply been injected with a special dye. This painful procedure causes harm and can be a source of infection. • Sunfishes feed exclusively on live food. The diet consists mainly of small fish and bottom invertebrates. A large amount of oxygen is required. Only dwarf Elassoma are completely harmless. Can coexist with large, but peaceful species.
Features of acquiring Monodactylids.
• Monodactylus (Psettus). They inhabit both marine water and brackish estuaries; only juveniles feel well in fresh water. Representatives of these families are often offered by specialized trade, but it should be noted that they are accustomed to living in brackish water. Monodactylus are not just accustomed to brackish water: they are also found in purely marine zones. However, juveniles of this species are offered in pet stores in purely fresh water. They can last there until they reach the size of a large coin, and at this growth stage, salt water needs to be added gradually. If the fish do not receive it “a pinch at a time”, they die when they reach the size of two large coins.
Features of acquiring Scatophagids.
• Scatophagus, Selenotoca. They grow up to 30 cm, live in schools, and feed predominantly on plants. Large, contrastingly colored fish that fit perfectly into the community of a spacious aquarium. They are very active and swim in different water layers, preferring open areas.
Features of acquiring Nandids.
• Badis, Monocirrhus, Polycentrus, Nandus. With few exceptions, these are predatory, strictly territorial fish that prefer dim lighting and planted areas. Small fish, usually with huge protrusible mouths, are true predators of amazing voracity. They attack chosen prey, which can be up to half the predator’s body size, with a sudden rush from hiding places. Given the above, it is advisable to keep these fish in a species aquarium.
Features of acquiring Gobies.
Only very few are suitable for a general aquarium. Most gobies are marine, many inhabit brackish and fresh waters of tropical and temperate zones. Freshwater gobies from the Gobiidae family are rarely imported, such as the spotted goby • (Stigmatogobius sadanundio) or Celebes goby (Stigmatogobius hoevenii). These small gobies do not grow larger than 4-5 cm and feed mainly on live food of all types and sizes that they can handle. Predators. Adult fish have a preference for animal food. They eat dry foods reluctantly or not at all.
Inactive, bottom-dwelling fish that love shelters show their best behavior when kept in a group in a species aquarium, which should feature rocks, caves, driftwood, and patches of plants. They prefer saline water; when kept in fresh water, they are more susceptible to diseases. • Bumblebee goby – Brachygobius xantozona. Brachygobius is unsuitable for community aquariums; a species aquarium is required.
Features of acquiring Melanotaeniid fishes.
• Bedotia; Chilatherina; Glossolepis; Melanotaenia; Rhadinocentrus; – 6-14 cm. Peaceful, schooling, active fish, mostly staying in the upper water layer, look spectacular in groups of 6-8 specimens, prone to jumping, like water movement, tolerate low oxygen poorly, and take food from the bottom reluctantly. Keep in schools in spacious aquariums, moderately planted and brightly lit; they do not touch plants. Ideal for co-keeping with medium-sized Malawi and Tanganyika cichlids, calming them down with their schooling behavior.
• Iriatherina; Kiunga; Marosatherina; Popondetta; Popondichthys; Pseudomugil; Telmatherina; – 3-5 cm. Keeping them is quite difficult. Most species in nature prefer to stay in the middle water layers of clear, oxygen-rich streams. These fish are constantly in motion. Completely harmless and easily get along with any small, peaceful fish.
Features of acquiring Pantodon buchholzi (butterflyfish).
10-12 cm. They have powerful pectoral fins, with the help of which they jump and glide through the air for distances up to 5 meters. Low aquariums (20-30 cm high) with a large bottom area should be used for keeping these fish, and they must be tightly covered with a glass lid. The gap between the water surface and the glass should be about 10-15 cm. Calm during the day, active in the evening, sometimes territorial skirmishes occur. Feeding them in aquariums is difficult.
Food must be live only – houseflies, fruit flies, cockroaches, mealworms, their larvae and pupae, phantom midge larvae (corethra), daphnia, and bloodworms (which need to be slightly dried to a “non-wetting” state); they also take small fish and large flakes of dry food. Any deterioration in water quality can lead to fin rot and loss of appetite. They are incompatible with other surface-dwelling fish, so it is recommended to keep them with larger, peaceful fish inhabiting the middle and lower levels of the aquarium. They can also show aggression towards members of their own family.
Features of acquiring Labyrinth fishes.
Features of acquiring catfishes. 
