Author Topic: How to Keep and Breed Peat (soil) Spawners  (Read 3955 times)


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How to Keep and Breed Peat (soil) Spawners
« on: August 13, 2012, 10:13:22 PM »
This information can be found in the American Killifish Association's "Beginner's Guide" at

Soil Spawners

In examining the breeding techniques applicable to the soil-spawners, the South American "diving" species will be set aside and described under "Peat Divers". The balance of the soil spawners will be divided into two basic categories:
Group "A" includes those killies that must undergo a drying period during incubation, this drying period being a clear-cut requirement for successful propagation. Such killifish are regarded as true "annual" fishes as the areas they inhabit dry up annually; when the rains come and the dry pools and streams fill again with water, the eggs which are embedded in the mud and silt hatch into fish that will mature, reproduce and die in less than one year! The genus Nothobranchius is the most common aquarium constituent of this group.

Group "B" includes killies whose eggs may also undergo a drying period, but this drying period is not a requirement for successful propagation; full-term water incubation in also acceptable. Many of the Fundulopanchax species follow this pattern, e.g. Fp. walkeri, Fp. filamentosus, Fp. sjoestedti and Fp. fallax. For the most part, this second group has a slightly extended life span and, in some cases, matures at a slower rate than do the true annuals.

The most frequently used spawning medium for Group "A" is peat moss. In addition, silica sand, green sand, crushed walnut shells and glass beads also have been used successfully. Eggs are laid directly over the medium and a strong flip of the male's caudal fin buries the egg just beneath the surface. The chief advantage of using one of the non-peat media is that the eggs are easily harvested and one can know exactly how many eggs are being stored. The disadvantage is that the eggs are sometimes damaged while being harvested. All that is necessary for harvesting the eggs is to sift the spawning medium through a net that is large enough to let the substrate fall through but still small enough to keep the eggs within it. Also of significance, especially for silica sand, is that due to the fact that the eggs are "packed" beneath the surface of the medium, little of the oxygen available in the water reaches the eggs, thus inhibiting any significant development. When the eggs are collected, almost all of them are in a similar stage of development. Rosario LaCorte is credited with introducing crushed walnut shell as a spawning medium for killifish. It has the advantage of containing lignin, a substance that stimulates spawning - also found in peat moss.

Despite the advantages of the other media, peat moss is recommended for group "B". This group of killies does not display quite the same ability to bury the eggs as do the true annual species. Consequently, a percentage of the eggs are laid simply to float freely, exposed to fungus spores and decaying food or waste materials. Peat moss will provide a far more penetrable medium. Another factor, certainly worth consideration, is that a good many of the species in Group "B" lay eggs that are light sensitive to some degree. Certainly a dark medium such as peat moss would be more protective to such eggs. Furthermore, the majority of Group "B" species prefer acid water conditions. The use of peat moss favors such a condition.

Many of the species in Group "B" will lay their eggs in bottom mops. If this method is employed it is recommended that the eggs be picked from the mop and placed on damp peat moss for incubation (the water vaporizing method, described earlier. This method has worked quite successfully with such species as Fp. monroviae, Fp. sjoestedti and Fp. filamentosus, to name a few.

For several of the soil spawning fishes, many specialists who raise large quantities of killies prefer to condition numerous males and females in separate containers and, on pair at a time, place them in the spawning tank. Due to heavy conditioning, the female is quite round with eggs when introduced with the male, but after 12 to 24 hours becomes "spawned out" and appears considerably thinner. This pair is then removed and a new pair introduced. This method has its merits as no feeding is done in the breeding tank, thus eliminating the chance of fungus due to decaying food and waste (especially important for Fp. occidentalis and Fp. toddi). The female, being quite uncomfortable with eggs, is receptive to the demands of the male, thus reducing any chance of severe disagreement.

Harvesting Eggs, Incubation and Fry

There are numerous ways in which eggs can be separated from silica sand, glass beads or crushed walnut shell. The method most common in practice is to vigorously agitate the medium, which quickly sinks while the lighter eggs swirl freely in the water. A fine-mesh net is passed through the water in a figure-eight pattern thus catching the floating eggs. This is repeated several times until most of the eggs are collected. It is best to immerse the eggs in a tray of shallow water containing a fungus preventative before placing in peat moss for incubation. The eggs are allowed to water incubate for several days giving opportunity to remove any eggs which are infertile or contaminated by fungus. When this short period period of water incubation is complete, a handful of peat moss is boiled and rinsed several times. The cool peat is placed in a towel and squeezed lightly to remove excess water. The peat should remain moist, but not so wet as to be able to easily squeeze water from it. The eggs are removed from the tray and placed in the peat being careful to distribute the eggs throughout. The peat is then placed in a plastic bag and sealed for the prescribed incubation period. For most species of Nothobranchius this period is from 60 - 75 days.

If peat moss is used as a medium, the peat is simply netted out, gently squeezed, and placed between two thick layers of newspaper. After a few hours, the newspaper will have absorbed most of the moisture from the peat. The peat may then be sealed in a small plastic bag. The bag should be clearly labeled with the name of the species, the date collected and, if desired, the hatching date. Storage can take place between 70 and 75 F, although some breeders of Nothobranchius prefer to incubate eggs at close to 80 F. Too high a temperature (over 80) will probably have an adverse effect on the eggs and any fry that hatch.

When the prescribed hatching date arrives or when sufficient embryonic development is noted in most of the eggs, hatching is achieved by placing the peat in a shallow tray or bowl. The water should be relatively soft and as close as possible to the chemical water conditions required by the fish that are to be hatched. A uniform hatching can be stimulated by vigorous agitation of the water and/or with the addition of a pinch of dry or liquid food. Many hobbyists use microworms to force hatching, as mentioned earlier.

Joe Ricco has shown that it is possible to speed up the development of annual eggs, especially those in the genus Nothobranchius. The eggs are placed in water and allowed to incubate at temperatures just below 80 F, until the embryo is clearly seen. At that point the eggs are stored in peat moss and given a dry period from 3 - 6 weeks. After the dry period, the peat moss and the eggs are hatched in the usual way. The resulting fry are perfectly healthy. It is possible to cut down the incubation period by many months using this method, but many eggs go bad along the way and the number of fry obtained is less than is the case when the regular storage method is used.

As soon as the eggs have hatched, the fry immediately begin to feed on the micro-organisms that are present in the water. Soon newly hatched brine shrimp can be offered. Growth of the young fish is phenomenal. In a short time the fry must be removed from their cramped quarters and placed into larger growing tanks. In approximately two or three weeks they are able to take sifted brine shrimp or daphnia. Even freshly chopped tubifex worms are relished. Almost without exception, in 6 - 12 weeks, the fry have grown to maturity .... the females fill with eggs, males fight .... and nature's cycle has again begun.

Peat Divers

Perhaps the most interesting and unique breeding behavior of all is displayed in the spawning behavior of certain South American species. Their behavior is unique in that a pair will completely burrow or "dive" into the bottom soil during the spawning process. These fishes are true annual species with eggs capable of surviving extremely long dry seasons. Development of the eggs is far from uniform; significant development of many eggs may be postponed for many months. There have been numerous reports that such eggs (called "resting" eggs) have incubated for as long as 24 months before full development had taken place. Perhaps this indicates the enormous capacity given to these fishes in order to survive extended dry periods.

Preparing the Breeding Aquarium

The most important factor in preparing the breeding aquaria for the peat-divers is the presence of a sufficient amount of spawning medium such that the fishes are able to burrow deeply. Peat, of course, is the best spawning medium. It should be boiled and rinsed thoroughly before use. The peat should cover the entire bottom of the breeding container. A 2 gallon drum-shaped bowl will serve admirably. The bottom, which tapers to a small area, required less peat that say a 3 gallon tank. If a larger aquarium is employed, a shallow bowl or dish filled with the prepared peat can be used. The pair, seeking the peat, will spawn in the confines of the dish or bowl. This container can be removed at intervals and the eggs collected without disturbing the fish.

Peat divers are best spawned in pairs or trios. Many successful breeders of these species condition males and females separately for four or five days, then place them together for two or three.

Harvesting Eggs, Incubation and Fry

Harvesting the eggs of the peat divers is rather standard to all soil spawners. The peat is netted out and placed between the layers of newspaper. Normal incubation is just slightly extended in relation to other soil-spawners. However, as mentioned before, it can continue for as long as two years before "resting" eggs are ready to hatch. After 75 - 90 days the peat may be examined and the eggs that show advanced development may be removed and hatched. Such eggs show a clearly defined eye on the embryo and are quite dark in color. The familiar "resting" eggs, still clear or translucent, can be left to incubate and to be checked at regular intervals for development.

Perhaps the most important advice that one can heed to ensure a successful hatching is this: collect the peat moss frequently, at least once every two weeks. The longer the peat moss is in the spawning tank the more decomposed food and waste the peat will contain. Eventually the eggs will become victims of this pollution. Relatively clean peat moss is of great importance to the successful development of annual eggs.

Hatching procedure are followed as explained for the other soil spawners. The fry are relatively large and can begin consuming newly-hatched brine shrimp immediately.
« Last Edit: August 27, 2012, 09:46:54 PM by azkillie »