Tumbling your Cichlid eggs can sometimes be a critical necessity, for instance, if your mouthbrooding female spits the eggs out before they have hatched or if you accidentally (or purposefully) strip the eggs from the female too early. In this article, we will discuss why you need to tumble your eggs, when to tumble them, and for how long.
Mouthbrooders differ from other egg-layers in that their eggs
are non-adhesive, whereas most substrate spawners’ eggs stick
to whatever they are laid on. Substrate spawn-ers, like most American
Cichlids and many Tanganyikans for example, will guard the eggs
after laying them and the female will fan the eggs by waving her
pectoral fins back and forth. In this way, the female increases
the oxygen available to the eggs. Mouthbrooders, on the other
hand, suck water through their mouths and over the eggs, gently
rotating them in their buccal cavity. The concept is essentially
the same: the eggs need lots of oxygen. If not, they will quickly
necrose and succumb to fungus and rot.
In 1954, the scientific community demonstrated just how vital the churning
action provided by mouthbrooding females is to the eggs. In an
experiment, Evelyn Shaw and Lester Aronson created large flows
of water over Tilapia macrocephela eggs. By placing them
in a special tube with slight depressions the eggs were not allowed
to “roll over” or tumble. The sides of the eggs exposed to the
current lived while those parts turned away from the flow died.
This experiment performed almost half a century ago clearly demonstrated
that the churning of the eggs in a mouthbrooder’s buccal cavity
is to expose all parts of the eggs to oxygenated water. This experiment
further demonstrated that the fungus that appears on dying eggs
is not what kills the egg, but is merely a secondary infection.
Now that we understand why Cichlid eggs need to be tumbled, let's talk when to tumble them. Female Cichlid mouthbrooders typically incubate their eggs for a period of 21-32 days, with 28 days being more typical. It usually takes the eggs 14-21 days to hatch. If you end up with eggs that have not yet hatched (either accidentally or purposefully) it will be imperative to tumble them. And even once their heads and tails have "popped out," I still would encourage you to tumble the eggs (perhaps a little less vigorously) until the fry can move around a bit. But for sure, once the fry are "free-swimming," tumbling is no longer necessary. At this point, the fry will still have their egg sac, which will take several more days to be completely absorbed. This egg sac contains their food source so you shouldn't feed them until this is gone.
The basic idea of tumbling your eggs is to gently rotate them. The simplest way to do this is to place them in a small container, which can then be placed inside a fish tank. Something with a rounded bottom is best because square containers often allow the eggs to get stuck in a corner. This container doesn't have to be very big. It could be a plastic soda bottle or even a food strainer (i.e., collander). I have found the best thing to use is an old undergravel filter lift tube. More on this later. Using an air tube (airstone is optional), I adjust the bubbler so that the eggs are barely moving. It is important that they not rest on the bottom. You don't want them bouncing hard, just gently moving. If you bounce them too hard, they will bruise and die. Remember, you are trying to simulate what the mother does for her eggs.
Here are a few tips that I have picked up along the way:
- Check on the eggs several times a day to make sure there aren't any dead fry or fungused eggs. This often happens if not all of the eggs were fertilized. If you find any dead fry or eggs, remove them right away to preven fungus from spreading and killing the rest of the brood.
- Be prepared to experiment and find a method that works best.
Do expect to keep all or any of the first couple attempts (and
you'll be happily surprised when you do!). Also, the eggs of
some species require a little different tumbling technique.
For instance, those who produce small eggs, like most Victorian
Haps, hatch best when they are gently bounced on the bottom
of the tumbler. Larger eggs, like those of C. frontosa,
Tropheus, and Cyprichromis should not bounce.
These hatch better if they are just gently moving on the bottom
of the tumbler, in a swaying motion. Mbuna eggs, I have learned,
are the most forgiving and do fine with either method.
- The time it takes to hatch is strongly dependent upon temperature. The higher the temp, the sooner they'll hatch. Be careful though, because the temperature also affects the speed with which the fungus grows and could potentially kill the whole brood. I suggest starting with a temperature of 78ºF for the first couple of days, watching for any dead or unfertilized eggs, and then slowly increasing the temperature to 80ºF - 82ºF. □