Not all mazes have to go to the surface of the water.
A lot of information states that labyrinth fish need to come to the surface to breathe or build their nests. This is true for many species. But there are almost as many types of labyrinths that do not have to go to the water surface at all or only very rarely. Some of these species tend to live in the lower water layers.
This includes all Parosphromenus species, the Parasphaerichthys species, the small red dwarf betta species, many smaller mouthbrooders, etc.
Species that have to come to the water surface live in nature in rather stagnant waters with a corresponding lack of oxygen, eg in rice fields. These species are foam nest builders rather than mouthbrooders.
However, dwarf gouramis, Parosphromenus, are known
rum foam nest builders, although they only come to the surface when something is wrong. However, these foam nests are more likely to be created in caves deep below the water surface.
Trichsopsis vittata likes to stay on the water surface. Tr. schalleri also tends to stay on the water surface. But Tr. pumila. They like to build their nests under leaves deep under the water surface
Betta splendens, Betta imbellis and Betta smaragdina live in more stagnant waters, although the rainy season brings variety. They often have to go to the surface of the water, but also only build their foam nests on the water surface.
Labyrinth fish need a lot of space.
Labyrinth fish can become aggressive, especially during the courtship and breeding season. Aggressiveness is often directed at other labyrinthists.
During the spawning preparations, the respective female is vigorously driven through the aquarium by the male. The female needs space to evade and places to hide to recover.
In tanks that are too small and without hiding places, females are often hunted to death. It is therefore often recommended to give the aquarium a strong structure and to provide hiding places. However, many aquarists do not realize that the animals have to become almost invisible, especially in small aquariums. As soon as a driving male sees or tracks down the female, the female is chased again.
Aggressiveness varies greatly from animal to animal. For example, while a pair of gourami is peaceful, another pair can hunt other fish, especially other labyrinths, to death.
Often at least some species of the labyrinth fish are described as peaceful, eg mosaic gouramis and dwarf gouramis. This usually only applies outside of the breeding season. These species also become aggressive during the breeding season.
In smaller aquariums, labyrinths are kept in pairs. Small groups are kept in large aquariums with, for example, 550 liters of water, so that possible aggression is spread over several animals.
Labyrinthine and CO2.
It is repeatedly claimed that fertilization with CO2 is dangerous for labyrinth fish. Because CO2 is heavier than air, CO2 can therefore settle on the water surface. If the aquarium has no cover, the CO2 will not be removed from the surface by air currents. Labyrinth fish can then no longer breathe on the surface.
However, numerous aquarists keep labyrinth fish without any problems despite fertilization with CO2. With sufficient ventilation and not too much CO2 fertilization, problems should not arise under any circumstances.
Covered aquariums are usually not so tightly closed that there are no air currents. Normally, even in aquariums with a cover, the CO2 is displaced from the water surface and no layer impermeable to air can form on the water.
Even the amount of CO2 generated is not enough for such a layer. Especially since the main part of CO2 should stay in the water so that the plants can use it. If a dangerous amount of CO2 were to reach the water surface, fertilization would be pointless.
Even if the fertilization is not switched off at night when the plants do not consume any CO2, no dangerous amounts are produced on the water surface. Assuming that about 20 bubbles make 1 cubic centimeter, then at 60 bubbles per minute 2.5 cubic centimeters of carbon dioxide are released into the aquarium. Even if no CO2 is dissolved in the water and all the CO2 comes to the surface, 150 cm cubic centimeters are created per hour. With 8 hours of darkness, 1200 cubic centimeters of gas or 1.2 liters are produced. In a small aquarium with a base area of 60×30 centimetres, 1.2 liters corresponds to a height of 6 millimetres. However, the aquarium is not airtight and the water absorbs part of the CO2. The amount of CO2 is therefore much lower than in this sample calculation.
Only a few species of labyrinth fish rely on constant surface breathing. A number of species only breathe through the labyrinth if there is too little oxygen in the water.
Because a whole series of coincidences must come together, possible problems due to a CO2 layer are probably only theoretically possible, but not to be expected in practice.
Isolated reports of labyrinth fish dying due to a CO2 layer on the water surface are very questionable. Other causes are possible and more likely.
Problems can arise from an incorrectly set and too strong CO2 system. Then labyrinth fish are not particularly affected, but all fish in the aquarium are endangered.