Bubble nests, also spelled bubblenests or bubble-nests, created by some fish species, are floating masses of bubbles blown with an oral secretion, saliva bubbles, and occasionally aquatic plants, or an area for egg deposit attached at the bottom. Fish that build and guard bubble nests are known as aphrophils. Aphrophils include gouramis (including Betta species) and the synbranchid eel Monopterus alba in Asia, Ctenopoma (Anabantidae), Polycentropsis (Nandidae), and Hepsetus odoe (the only member of Hepsetidae) in Africa, and callichthyines and the electric eel in South America. Most, if not all, fish that construct floating bubble nests live in tropical, oxygen-depleted standing waters. Also, some sunfish and cichlids create bubblenests. Anabantidae are the most commonly recognized family of bubblenest makers. The nests are constructed as a place for fertilized eggs to be deposited while incubating and guarded by the male until the fry hatch.
Bubble nests are built even when not in presence of female or fry (though often a female swimming past will trigger the frantic construction of the nest). Males will build bubble nests of various sizes and thicknesses, depending on the male's territory and personality. Some males build constantly, some occasionally, some when introduced to a female and some do not even begin until after spawning. Some nests will be large, some small, some thick.
Various things have been shown to stimulate bubble nest construction, such as quick temperature changes, barometric changes, fluctuations in rainfall, materials in the tank, and presence of other males or females.
The nests are built by the male (sometimes females) and their size, position and shape depends on the species. They are often built near an object that breaks the surface of the water, which forms a base for the nest.
Bubble nests created by male Siamese fighting fish (Betta splendens) are made from air bubbles coated with saliva to increase durability. The creation of the bubbles is audible and often frantic.
Bubble nests and breeding 
All species of bubble nesters continue parental care after construction of the floating bubble nest and spawning. After spawning, the eggs float up into the bubble nest, or are carried there, held in the mouth by the male. The male lodges them in the nest to protect them, and then protects the brood by chasing away the female and any other intruders, concentrating on the eggs in the nest, retrieving any eggs or fry that fall from the nest and keeping the nest in repair. The male will guard the eggs constantly until the fry hatch in 24–48 hours and be suspended from the nest. For the next few weeks, they will stay nearby being tended by the male.
See also 
||This article needs additional citations for verification. (August 2007)|
- Hostache, Gérard; Mol, Jan H. (1998). "Reproductive biology of the neotropical amoured catfish Hoplosternum littorale (Siluriformes - Callichthyidae): a synthesis stressing the role of the floating bubble nest". Aquat. Living Resour. 11 (3): 173–185. doi:10.1016/S0990-7440(98)80114-9.
|Wikimedia Commons has media related to: Bubble nests|
-  - A video of two Siamese fighting fish spawning. The male can be seen carrying eggs up to the bubble nest.
- Bubble-nest building
- Betta fish bubble nests and pet care
- Function of bubble nests