Spawning occurs during the daytime. There is indication that the female drinks the sperm and that fertilization takes place after the sperm has passed through her digestive tract. The male and female form the "T-position", where the female places its mouth over the male's genital opening and collects the sperm in the mouth. The female rests at the bottom for 30–60 seconds, and then swims to the nest, turns upside down, and lays the eggs in the nest. "H. littorale" is a multiple spawner. Investing in reproduction is high in females since they can spawn up to 14 times during a 7-month breeding season and each spawn consists of 6,000–9,000 eggs. On average, two to four females spawn simultaneously, resulting in an average number of 20,000 eggs per nest. The adhesive eggs are located in the centre of the nest under the plant debris above the surface of the water, and not in contact with the oxygen-depleted swamp water. The male guards the nest during incubation; incubation of the eggs takes two to three days depending on the temperature in the nest. The male also regularly supplies foam to the nest. Guarding and maintenance of the nest occurs day and night. Once spawning has been completed, the male attacks females that have deposited their eggs in the nest. Despite intense predation pressure on eggs and larvae, the male's guarding behavior extends for only one or two days after hatching. The male attacks with its large pectoral spines erect; the attack consists of rapid propulsion towards its target followed by a sharp lateral turn, which causes the rough outer edge of pectoral spine to drag across the target and cause abrasion.