Moving clownfish eggs (arrow) laid on a tile into a rearing tub with an
airstone to keep fungus from developing.
attempting to breed. The one absolute key to proper incubation is water
circulation. It must force fresh, oxygenated water over and through the
egg mass so that each egg is effectively kept clean and incubated. Many
methods exist to incubate a spawn. Ideally, an incubator should mimic the
role of the male fish.
7 Reasons Brooding Males
In order for captive males to successfully incubate clutches of eggs to term they must feel secure in
their environment. Often due to a variety of factors
males prove unreliable and either abandon their
broods or consume them.
1. Broodstock tank too small or too little
shelter areas present
2. Inadequate light cycle
3. Inadequate feeding cycle/diet
4. Poor tank positioning
5. Outside disturbance
6. Poor broodstock
7. Inexperience—first spawns
Water vs. Air for Incubation
Incubating marine fish eggs is often a difficult task, but with creativity
and a wealth of products available, creating a simple incubation device can
be uncomplicated. Air pumps are ubiquitous and it seems every aquarist
has a few lying around. Incubating demersal eggs from groups such as
the clownfish, gobies, blennies and damsels poses few difficulties if they
are moved as close to hatching as possible. They can be incubated with a
moderate flow of bubbles rising across the eggs.
For most demersal spawning fishes, air movement offers a random motion
of bubbles and water currents over the eggs. The size of bubbles rising from
an airstone is generally not uniform and each bubble is highly influenced
by the flow of water created by others rising nearby. In this way, rising air
bubbles tend to wander side to side as they move up the water column.
As they crisscross the eggs, dead spots (with poor water movement) are
eliminated and agitation is more successful.
However, air is limited in its applications as it will only travel in one
direction—up. In many instances, eggs are spawned in a flower pot, on a
Artificial incubation of damselfish eggs in a short section of pipe. Note
gentle flow of air bubbles that keep eggs healthy.
standpipe or on a heater tube. Eggs spawned on the inside roof of a flower
pot, for instance, are difficult to incubate with air. Air can be forced to rise in
an angled direction as on a ceramic tile, but it proves very difficult to harness
in a sharp corner without creating air pockets and uneven flow patterns.
For these and other odd situations, moving water can be equally or more
effective for short-term incubation. The water flow from a powerhead can
be diverted to a plastic airline gang valve or similar valve system to regulate
the flow of water through a piece of airline tubing. Several of these water
jets can be aimed to provide a continuous flow of water over a mass of eggs.
Randomly moving the waterflow several times daily will increase the efficacy
of incubation and prevent dead spots from developing within the egg mass.
The use of water is often necessary to incubate eggs. Eggs placed in
difficult-to-access corners of flowerpots are one example. Dottyback eggs
similarly must be incubated with water, as small air bubbles quickly become
lodged within the sticky egg mass.
Egg tumblers for species that produce a ball or mass of eggs (rather than
attaching them to hard substrate) can be created in a number of different
ways, but all have the same goal. The idea is to keep the egg mass in constant
slow motion, rolling around in a small area.
A length of thin-wall clear plastic undergravel lift tubing (approximately
3/4-inch in diameter) can be cut into two separate sections. One section is
heated with a cigarette lighter and molded over the other section so a tight
coupling is created. A small section of mesh (a piece of mesh from a fish net
works well) is inserted between the two pieces of clear pipe. On the bottom
end of this tumbler, a diaphragm from an air pump, a soda bottle cap or
similar PVC fitting is used to cover the bottom-end section of pipe, making
it leak-proof. A short length of rigid airline tubing is inserted into a hole
drilled in the cap or in the case of the rubber diaphragm the existing hole.
The rigid airline tubing is connected to a gang valve and subsequently to
a powerhead or small water pump. Aquarium heater suction cups fit the
diameter of the undergravel lift tube and work well to hold the tumbler
vertical and stationary. The egg mass sits on the screen on the top part of the
tumbler, and water is forced up through the bottom. In this way, the water
flow is adjusted so the eggs tumble slowly. Water must not be pumped at too
high a level to cause the egg mass to exit the top of the tumbler.
Ideally, the tumbler would be situated in a rearing tank connected to a
central filtration system. Water entering the tumbler would come directly