The diet of this genus is typical for a Loricariid – algae and aufwuchs.
Bristlenoses do not school but hide when not feeding, juveniles however are typically found in brightly lit shallows at the water margin making them susceptible to predation by birds.

Ancistrus species have the capability of obtaining oxygen through their modified stomach.
This allows them to survive in conditions with low oxygen levels.

Breeding takes place in hollows, caves and mud holes in banks.
Males may clean the inside of the cavity with their suckermouth before allowing the female to approach and inspect the nest.
 Courtship includes expanding the dorsal and caudal fins and attempts by the male to escort the female to the nest.
While the female inspects the nest, the male keeps close contact.
The female may lay 20–200 adhesive eggs, usually to the ceiling of the cavity.

The female plays no role in parental care; the male takes care of its young.
Males will clean the eggs and the cavity with its fins and mouth.
Males inspect eggs to remove diseased or infertile eggs, and aerates the clutch by fanning them with its pectoral and pelvic fins.
During this time, a male usually will not leave the cavity to feed, or will leave only occasionally and quickly return.
The eggs hatch in 4–10 days over a period of 2–6 hours; the male guards the eggs for 7–10 days after hatching.
The fry remain in the cave, attaching to the walls and ceiling with their mouths, absorbing their yolk sac in 2–4 days and becoming free swimming.

Males of these species are competitive and territorial.
Males display to each other by positioning themselves parallel to each other, head to tail, with dorsal and caudal fins erect and cheek odontode spines everted.
If this escalates to combat, the males will circle each other and direct attacks at the head.
If an intruding male manages to evict another male from the nest, it may cannibalize the other male's young.

A male bristlenose may guard several clutches of eggs simultaneously.
Females prefer males that are already protecting eggs and may prefer males that are protecting larvae; it has been suggested that the tentacles may act as a fry mimic to attract females, which would allow males without eggs in their nest to compete with males guarding eggs.
Several clutches in various states of development from eggs to free-swimming larvae can be found in one nest.
The diet of this genus is typical for a Loricariid – algae and aufwuchs. Bristlenoses do not school but hide when not feeding, juveniles however are typically found in brightly lit shallows at the water margin making them susceptible to predation by birds.
Ancistrus species have the capability of obtaining oxygen through their modified stomach. This allows them to survive in conditions with low oxygen levels.
Breeding takes place in hollows, caves and mud holes in banks. Males may clean the inside of the cavity with their suckermouth before allowing the female to approach and inspect the nest.  Courtship includes expanding the dorsal and caudal fins and attempts by the male to escort the female to the nest. While the female inspects the nest, the male keeps close contact. The female may lay 20–200 adhesive eggs, usually to the ceiling of the cavity.
The female plays no role in parental care; the male takes care of its young. Males will clean the eggs and the cavity with its fins and mouth. Males inspect eggs to remove diseased or infertile eggs, and aerates the clutch by fanning them with its pectoral and pelvic fins. During this time, a male usually will not leave the cavity to feed, or will leave only occasionally and quickly return. The eggs hatch in 4–10 days over a period of 2–6 hours; the male guards the eggs for 7–10 days after hatching. The fry remain in the cave, attaching to the walls and ceiling with their mouths, absorbing their yolk sac in 2–4 days and becoming free swimming.
Males of these species are competitive and territorial. Males display to each other by positioning themselves parallel to each other, head to tail, with dorsal and caudal fins erect and cheek odontode spines everted. If this escalates to combat, the males will circle each other and direct attacks at the head. If an intruding male manages to evict another male from the nest, it may cannibalize the other male's young.
A male bristlenose may guard several clutches of eggs simultaneously. Females prefer males that are already protecting eggs and may prefer males that are protecting larvae; it has been suggested that the tentacles may act as a fry mimic to attract females, which would allow males without eggs in their nest to compete with males guarding eggs. Several clutches in various states of development from eggs to free-swimming larvae can be found in one nest.
Ancistrus