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01. Modern Aquarium
02. Anatomy + Physiology
03. Feeding Fishes
04. Aquarium Principles
05. The Tank
06. Lighting + Heating
07. Aeration + Filtration
08. Aquarium Rooms
09. Breeding Livebearers
10. Egg Scatterers
11. Anabantids + Cichlids
12. Feeding + Rearing
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Breeding the Egg Scatterers
The egg laying fishes are quite a different proposition from the livebearers when it comes to breeding. They are a more immediate nuisance but ultimately less trouble. That is to say, induction of spawning and coping with it needs more preparation as does feeding and raising the young, but, when all that is over, the adults can be kept in communities and will generally only spawn to order.
The egg scatterers include most aquarium fishes—the Characidae, the Cyprinidae, and the Cyprinodontidae. Most, like the goldfish, lay adhesive eggs, which stick to plants, but some like the zebra fish, lay non-adhesive eggs, which fall to the bottom. Nearly all eat their eggs if given the chance. The typical spawning movement is a chase of the female by the male, accompanied by spasms of egg-laying and simultaneous sperm ejection and fertilization. Activity may continue for an hour or for several days, but a few hours is the general rule.
Once livebearer young have been produced and saved from parental cannibalism, the battle is practically over. Once the eggs of an egglaying fish have been deposited, and this may be no mean accomplishment, the battle has just begun. The eggs must be preserved from predators and disease, they must hatch, and the young must then be protected, fed and raised. Feeding may be the worst problem, but predators run a close second. Thus, although a successful spawning and raising of an egg-laying species may occur in an unprepared tank, it usually does not. It is all a question of percentage of successes. Many methods for the spawning and raising of different species are described in the literature, and the most that can be said for the majority of them is that Mr. A. did succeed (usually on one occasion only) in breeding species X by such and such a method. No one, (with the exception, perhaps, of a few professionals) knows how often this method will succeed or how good it is compared with the method of Mr. B, which also succeeded once or twice.
It is therefore necessary, especially with the egg scatterers, to list a number of general principles which are pretty clearly established, to indicate how improvements may be made in the future, and above all to recommend an experimental approach. Perhaps the best general advice is that few species are actually as particular about conditions for successful spawning as most people think, and that cleanliness, healthy fish, and proper feeding are usually more important than fussing about with pH, temperature, light, and shade, and so forth. (Note the word "usually"—exceptions occur.)
Sex in Egg Scatterers
The majority of egg scatterers have distinguishable sexes, even out of the breeding time, and nearly all can be told apart quite easily when the female fills with roe. The standard books on fish varieties should be consulted for details of the various ways in which sex can be told. Where these do not help, it pays to remember that the male is often the slimmer and rather smaller fish and brighter colored. In the Characidae he usually has minute hooks on the lower part of the anal fin. These may sometimes be seen as a marking on the fin, or they may actually catch in a fine net and be quite a nuisance. In the Cyprinidae,
the breeding males often develop small white pearly dots on some part (as on the gill covers of goldfish). Most of the barbs show color differences between the sexes, and they are very easy to sex for that reason. In the Cyprinodontidac, color differences are again the rule, which facilitates matters for the tyro provided some of each sex are present.
Determining sex early and out of the breeding time or before maturity is of course important when selecting fishes for future spawning. With practice, it is surprising how easy it is to sex a species which would baffle an amateur even when he knows what to look for.
Cleaning Tanks
Tanks for spawning egg scatterers must be clean, preferably newly washed out and disinfected, but at least cleared of all muck, snails, leeches, hydra, and so forth. It is virtually impossible to do this without a thorough cleaning. It is very difficult to clean and disinfect a planted tank without removing plants and sand, unless one risks killing the plants; it is best to use unplanted spawning vessels. The fishes don't mind. They don't appreciate the beauty of a well set-up tank with rocks and sand and plants and are just as ready to spawn in a bare tank, with a little weed anchored in an appropriate spot to receive the eggs. In fact, many will spawn in a completely bare tank, but they are much too likely to eat their eggs under these conditions.
As remarked above, many spawnings are brought through in planted, relatively dirty aquaria, for many enthusiasts actually advocate the presence of plenty of infusoria-producing material. What really matters are the chances of success and the proportion of eggs hatched and of young likely to be raised. One method may work once in three times and produce an average of 3 0 fishes a time—another will work two times out of three and produce 200 fishes a time (hence it is more than ten times as good a method). The clean method, with washed tanks and weed, is good, although no one has yet published comparative figures to prove statistically just how good it is.
The tank may be washed with warm water at about 120°F., care being taken not to crack heavy or plate glass. The water is best introduced gradually in order to displace existing water and to raise the temperature fairly slowly. Small tanks with thin glass can be treated much less carefully. The warm water should come well up under the top rim, so as to catch hidden pests. The water at 120°F. is left to cool of its own accord; dead snails, leeches, hydra, etc., are then siphoned off, and the volume is made up with tap water. Alternatively, the tank may be emptied and washed out or thoroughly rinsed with sea water or with 3 to 6% salt solution. This kills off most pests in a minute or two, as long as operculum-possessing snails are not present. The tank may be similarly rinsed with 70% alcohol (which may dissolve paint or even putty of some types). It may even be very thoroughly washed and scrubbed with cold water. Other methods are safer, since cracks are hard to clean out. Drying a tank for a few days is not a good method, for many pests or their eggs may survive.
Plants may be cleaned by a thorough washing under a brisk cold tap, followed by a 1/4-minute dunk in sea water or 3% salt solution and then a further brisk wash in cold water. They can be placed in water at 105°F. and left, but this will not kill all parasites and the higher temperatures may kill the plants; 120°F. will certainly kill them if left for an effective period. Instead of plants, artificial spawning media may be used that can be sterilized if necessary.
Cotton wool, wood wool, old rags, and dried seaweed of certain types are sometimes satisfactory, but it cannot be said that the results are in most instances as good as with plants.
It is possible to use potassium permanganate or other disinfectants for cleaning both tanks and plants, but in effective strengths they are often a nuisance and kill the plants. The concentrations of permanganate frequently advocated for use in aquaria, 1/4 to 3/4grain per gallon, are not effective for this purpose. Effective strengths of common disinfectants are costly and rather difficult to get rid of satisfactorily. Although the residue left in the tank may be harmless, it is likely to affect the fishes and to inhibit spawning unless an inordinate amount of washing-out is done.
Setting Up Tanks
Suitable tank sizes for the egg scatterers are 3 to 15 gallons for tropicals, according to the size and nature of the fishes, with larger tanks for goldfish. Small light tanks are more easily cleaned and set up than heavy ones, and since we are not concerned with cultivating infusoria in them their size matters little at the spawning stage, as long as there is room for the parent fishes to follow their particular routine. Later, the fry can be moved to a larger tank.
Most characins, small cyprinids, and cyprinodonts can be spawned in a 3-gallon tank (14 inches in length). For the usual scatterer of adhesive eggs, a bunch of fine-leaved plants or algae, or both intermingled, is placed in about the center of the tank and weighed down with a small stone. There should be room for the fishes to swim around and over this bunch of weeds. Suitable plants are Myriophyllum, Ambulia, Nitella, and the thread-like green algae. Anacharis is particularly unsuitable since it dies readily after most available disinfection methods, except for plain washing.
The medium barbs, like Barbus conchonius or B. ticto, should have somewhat larger, say, 6-gallon tanks, otherwise similarly arranged. This size is suitable for the danios, although those that scatter nonadhesive eggs require a different setup. Only really large fishes like the goldfish require big tanks, and it is surprising what can be done with a 10- to 15-gallon tank, even with these.
A dividing glass with rubber-covered edges (as for the top of the tank when a flush cover is used) is useful for some varieties. This is used for separating the fishes before spawning is required. Adequate illumination must be provided, since many fishes, especially cyprinodonts, like a well-lit spawning area. It is now the custom of some European aquarists to use a spotlight, illuminating only an area of the tank over the weeds, in which the fishes will come and spawn. Tanks should also have means for controlling temperature individually as it will sometimes be necessary to raise or lower it to produce the re- quired results.
Tanks prepared for fishes which lay their eggs on floating weeds, such as the panchax group, are similar to those above, but the weed is not anchored down. It is preferable to use well-washed Riccia, Salvinia, or other naturally floating plants, or they may sink to the bottom even if not weighted down.
Spawning
If the fishes are kept at an average temperature of 75°F., the ma- jority will spawn without a rise in temperature. All that is necessary is to place a ripe pair into the spawning tank with as little disturbance as possible. The tank should normally be filled nearly to the top with fairly new, but conditioned water. Exceptions to this rule are few; these include Hyphessobrycon pulchripinnis (lemon tetra), Neole- bias species. Brachydanio nigrofasciatus, Rasbora heteromorpha, and some of the barbs, notably B. everetti, B. nigrofasciatus, and B. tetrazoiia. All these are said to do better if the temperature is raised to about 80°F. On the other hand there is good evidence that Rasbora triliweata and Tavichthys albonubes spawn well at 70°F., and that
the latter does not like a higher temperature. The common goldfish (Carrasius auratus) spawns at about 70°F. and, in common with a few other species, may be stimulated to spawn by a slight jail in temperature. Many of these fishes will spawn at lower temperatures in open pools.
The pair of fishes placed in the breeding tank must be ready to spawn. For this, they are best conditioned for a week or so before with live food, although many species do not always require this procedure. The female should be full of spawn, bulging, but not left too long, or the eggs may not be fertile and she may become egg-bound and die. A thin female will sometimes spawn, but usually she gives few eggs; if she has a normal quota, she will not be thin. The male should look pert and well-colored. He may pale off on being moved, but he should rapidly regain his form, even within a few minutes.
Young males may not fertilize all the eggs and young females will not give a very large number of eggs, but there is no other reason why they should not be spawned. Keeping fishes for 2 years before spawning, when they are ready at 6 months, is pure waste and may create the many difficulties that occur when they are spawned later. Fish should spawn early and spawn regularly for the best results. Often, a female will be ready every 10 to 14 days and a male twice as fre quently. Do not chase the prospective breeding pair all over their tank to catch them and then expect them to spawn immediately. They will be too scared in most cases.
The fishes may spawn immediately, or they may wait several days, but somebody must be ready at frequent intervals to inspect the tank and remove the fishes if they have spawned. It is best to watch the whole process and take them out as soon as spawning is over, since they must be removed immediately or there may be few eggs uneaten. Even flooding the tank with live food does not always prevent egg eating, although it may help. Food should not be given during spawning, for it may terminate the process.
If fishes do not spawn quickly, they may do so early the next morning; therefore be up within 2 hours of dawn, or cover the tank so that it will stay dark and daylight may be admitted at your convenience. Alternatively, place the glass divider in position with one fish on each side of it and let them contemplate each other for a spell.
This often helps, so much that some breeders use the device regularly for a few hours or days before allowing the pair to come together. It is unnecessary in most instances, however.
If the fishes have not spawned within 2 days, gradually raise the temperature by 4° or 5°F. This often stimulates spawning quite promptly, but wait for another day or so if nothing happens. If spawning has still not occurred after 3 or 4 days, it is usually best to remove the pair, separate them, or place them in a large community tank, and try again a few days later. If they are kept in the spawning tank for more than 2 days, they should be given live food in moderation.
Variations on the above procedure include the routine placing of breeders in the tank after dark to induce spawning the next morning, placing the female in about half a day ahead of the male, and placing two males with one female in the case of many characins and the danios. This is thought to increase the percentage of fertilized eggs, but it is a rather hazardous procedure in many cases, as the males seem to spend more time chasing each other than chasing the female.
The spawning action varies with the species. Most of them indulge in the typical chase of the female by the male, but some start with the reverse procedure, and the female chases the male. This is often seen in Hemigrammus ocellifer (head and tail light fish) and in Barbus tetrazona (Sumatra barb). Finally, however, it is the male who chases; he takes up a position beside the female and in or over the plant mass, with a quivering motion, the eggs and milt are released. Some species have spectacular habits at the moment of spawning. The glowlight tetra {Hyphessobrycon gracilis) pair does a complete barrel-roll, the giant danio (Danio malabaricus) female whirls around several times in a horizontal plane, the female Rasbora heteromorpha loops the loop vertically, depositing eggs on the underside of plants as she does so. In this species, as in many others, the male clasps the female in a crescentric embrace, if the phrase may be allowed. He curls his body around hers and releases the milt as she spawns.
Aberrant Types
The above account covers many of the egg scatterers which lay adhesive eggs. A few lay non-adhesive eggs, outstanding among which is Brachydania rerio (zebra fish). With this fish, and with the related fishes B. nigrofasciatus and B. albolineatus (pearl danio), it is necessary to catch the eggs as they fall, to prevent their being eaten. This may be done by coating the bottom of the tank with small marbles or pebbles, preferably interlaced with plants, or by means of a grid of glass rods or other material which will allow the eggs to fall beneath and prevent the parents from following. Fairly shallow water, not
more than 6 inches, is also to be recommended, since it prevents the adults from having too long a time in which to chase and eat the falling eggs, as they tend to spawn near the surface.
Copeina arnoldi lays adhesive spawn above the water line and should be given a sheet of sanded glass or similar material projecting several inches into the air, and slanting at an angle of about 45°. The fishes leap into the air and deposit the eggs some 2 inches above the top of the water; these are guarded by the male from some distance off, and at frequent intervals he dashes over and splashes them with water. Lucidly for him, they hatch in about 24 hours.
The bloodfin (Aphyocharax rubripinnis) may also leap out of the water when spawning, but the eggs fall back into the water and, being non-adhesive, sink to the bottom, as with brachydanios. The croaking tetra (Glandulocauda inequalis) was a puzzle to breeders for a long time until it was found that a normal-appearing courtship is not followed immediately by egg laying. This occurs a day or so later, in the absence of the male, when the female deposits fertile eggs singly on the leaves of plants. This fish gets its name from the noise made by males.
A number of fishes are community breeders, spawning in large groups of mixed sexes. This happens with some of the barbs, such as B. conchonius and B. ticto, but they are also able to spawn in pairs. Some of the rasboras are much more choosy and very rarely spawn except in communities. Rasbora heteromorpha will spawn fairly readily when at least 8 or 12 fishes are present and very readily in communities of larger size, when unfortunately the eggs are nearly all consumed on the spot by the onlookers. The best results so far have been reported with the smaller groups, placed in planted tanks so that their habit of depositing eggs on the underside of growing plants can be practiced. Breeders are removed as soon as activity ceases or as soon as any of the fishes present begin to eat the eggs.
Goldfishes spawn with a grand chase in true carp fashion but have no special requirements except reasonable space. The hardier varieties will spawn at 60° to 65 °F. or even lower, but the fancy types are said to need 70°F. or thereabouts. They need more plants on which to spawn than most tropicals, and again two males to a female are often advocated.
Many of the characins have the reputation of being difficult to spawn unless there are a number of each sex which can be observed so that compatible pairs may be selected. It is stated, particularly by European breeders, that success with glowlight and neon tetras (Hyphessobrycon gracilis and H. innesi) can be expected only in such circumstances and in soft water. This is certainly not true of the glowlight, which can be spawned readily in standard conditions. The author's present experience with neons indicates the same, except that the eggs do not necessarily hatch unless in very soft water. Other myths about characins include the supposed necessity for dim lighting during spawning for some, very careful approach to the tank, and a dull-colored base in the tank. Although spawning fishes are likely to be disturbed if you jump and shout in front of them, they do not take much notice of any normal movement and seem to be singularly unaffected by the appearance of their tank. If the light is good enough for them to see, they will probably spawn, although there are exceptions, as we have noted. If the bottom of the tank is completely clear, they may be upset by the unusual lighting conditions and may even swim sideways or at an odd angle. In many cases this does not interfere with spawning, but with particularly touchy species it may matter, or with species like Barbus hexazona, which is very sensitive to the angle of illumination.
Cyprinodont fishes, whose eggs do not hatch for a long time, sometimes spawn over long periods and may be left with their eggs until the earliest begin to hatch. They do not eat the eggs, although they will eat the young. Thus, the panchax group may be spawned for 10 to 12 days; each female will lay about 20 eggs per day, and it is common practice to mate two females with one male. The eggs remain in the top weed and are not touched.
Their cousins, the bottom spawners, may have a very curious spawning history. The Argentine pearl fish (Cynolebias bellottit) breeds naturally in muddy places which dry up, and its eggs hatch out weeks or months later when water returns. This process has been successfully imitated in the aquarium.
Incubation of the Eggs
The great majority of fish eggs hatch in one day or less at 75° to 80°F. It is best to keep the temperature at the same level as when spawning occurred; however, fish eggs can stand fluctuations quite well, but in this case downward better than upward. The same is true of young fry. There are many reports of characin eggs taking 2 or 3 days to hatch, and, although some are undoubtedly correct, it still remains true that the majority of young are hatched within the first day. They are often difficult to see, and it may be 2 or 3 days before they hang on the glass, or on plants, and become easier to find; thus, it is easy to get the impression that they have not hatched out for longer than is the case. Most barbs are out by 24 to 36 hours, taking perhaps a little longer than the typical characin. Brachydanios take about 3 days, as do Copeina arnoldi and some of the pencil fishes (Nannostomus). Cyprinodonts usually take much longer, 2 weeks. Most Aphyosemion species and the panchax group take 2 weeks; Rividus species and bluefins (Chriopeops goodei), 10 to 13 days; the bottom breeders of this family, some of the fundalopanchax group, may take 7 to 16 weeks, according to temperature. Oddly enough, it is stated that, the higher the temperature, the longer these fishes take to hatch, thus at 70°F. they take 7 weeks, and at 78°F., 16 weeks. At lower temperatures, most eggs certainly take longer to hatch, and, since they will survive better than the fishes would, it is possible to ship fish eggs without elaborate precautions. Little use has been made of this procedure so far, and numerous snags will no doubt emerge when it is attempted on any scale, but the fascinating possibility remains that in the not very distant future the large lagged shipping can will be replaced by a small vial of fertile eggs.
After spawning is completed, eggs should be sought in the tank. They may be attached to weeds or appear like very small glass beads on the bottom. They should remain clear, and the development of the embryo should be watched to check that all is well. Infertile eggs quickly become opaque and fungused, looking like powder-puffs, with white filaments of fungus sprouting in all directions. Fertile eggs lying next to a mass of fungus-covered infertiles may be attacked, but they usually remain unaffected. It is tedious but not impossible to pipette off the fungused eggs. However, it is not really necessary in most instances.
If you cannot see the eggs, don't despair, as they are hard to spot until you are used to it, and sometimes even then. Once you have observed those of a particular species, it will be much easier to see them the next time.
Hatching
When the eggs hatch, the young fry still have a yolk sac, containing the remains of the nourishment of the egg. On this they live for a short time, sometimes only 1 or 2 days, sometimes as long as 5 days, before taking other food. For the first half-day or day they often remain quietly at the bottom of the tank, or in the weeds. In some species they take flea-like hops up into the water, sinking back again after wards. In practically all species they then attach themselves to the glass or to weeds or both, hanging motionless for an additional 1 or 2 days, still not feeding. They may also hang under the surface film of the water, and they frequently start on the glass and then transfer to the surface film. Finally the yolk sac is absorbed and they swim freely in the water, hugging the bottom or weed clumps in daylight and spreading all over the tank at night, or in the dark.
At the stage when the fry cling to the glass, it is easy to see them in the right light, which is preferably from behind or the side. They cling head-upward and each is visible as a little glass splinter with a fat tummy (the yolk sac) and two very large eyes. Watch the yolk sac go down, for when it does, the time to feed is near. In the later, free-swimming stage, they are less easily seen, and the best time is at night. Use a torch or a hand-lamp of some kind and send a gentle 'beam cross the tank from one side; the fry will be seen swimming in midwater. They may be counted with fair accuracy at this stage, or at he clinging stage before it. The best way to count is to choose a ypical section of the tank and count it carefully, then multiply by
the figure representing the relative size of the section to the tank as a whole. It is good practice to make this count, so as to check what is happening later on and to estimate food requirements. With practice, a good look at the tank of fry will enable you to guess with sufficient accuracy, to within 25 or 30%.