Last Updated: 4/18/12
Types of Breeding Strategies
Spawning Sites and Mops for Egg-Scatterers
*For information on breeding specific fish, see the list of fish I have breeding information on on my fish index.
Check out the pond egg identification guide if you have pond eggs and do not know what they are.
Note: Due to a faulty computer drive that replaced various symbols with strange symbols or deleted or added letters, this page may contain spelling errors and other errors that I have missed and have yet to correct. Please let me know if you find any. Thanks.
I really need to update this page. One day, one day! I am sorry that I do not have time.
Goldfish Breeding - on its own page
Brood or egg care versus none:
Some species of fish care for either their eggs and fry or both. Other species just dump the eggs and leave or eat most of them and surviving fry. The species that care for their eggs and fry include most cichlids. In fact, that is what they are known for. Many species of cichlid fiercely protect their eggs and fry from all other fish. Discus (a cichlid) fry even feed off of the parents' bodies. In some cases of egg and fry care, one parent does the job. In other cases, only one parent does (female for livebearers and most mouthbrooding cichlids and male for labyrinth fish and most substrate spawning cichlids). The male fathead minnow is one non-cichlid that cares for its eggs but not the fry. Some species like mouthbrooders and labyrinth fish protect their eggs very well. The livebearing fish protect their eggs the most, inside their bodies. Most species of fish dump and run or spawn and pig-out. Species that spawn and then eat their eggs and fry include goldfish, koi, danios, barbs, white clouds, and too many to list. Fish that eat their eggs make up for the loss by producing many more eggs than species that care for their young.
Egg scatterers swim into clumps of plants or along the sides of objects or even just in the gravel and spray eggs on them. The male and female will push against each other and wiggle as they release sperm and eggs. A good spawning medium for egg scatterers is java moss or artificial spawning mops. Some species of egg scatterers include most barbs, tetras, and danios.
Egg depositors lay eggs on a surface or in a nest. Some lay eggs under a rock or plant leaf like the fathead minnow, who will also use a broken flower pot. Others lay on the top surfaces of rocks or plants like angelfish. Some fish lay in gravel pits in a sort of nest like some species of cichlids. Some fish, like otocinclus, lay all around the surfaces of small plants. Cories and other fish may stick eggs to vertical glass as well as on plants and ornaments. The labyrinth fish lay in a bubble nest (see below).
Live bearers are a special case. Species include guppies, mollies, swordtails, platies, halfbeaks, mosquito fish, and more. The males use a gonopodium which is a modified anal fin to inject their sperm directly into the females. She carries her eggs inside her body where they develop. She can raise several batches from one mating several weeks earlier. The fry are born live. These fry have the ultimate pre-natal care but once born are on their own.
Most labyrinth fish, or anabantoids, make bubble nests. Males make the foamy nests by blowing bubbles of saliva and air onto the surface of still water with floating plants to hold the nest together. He defends the nest until the fry are born from other males and females that are not ready to spawn. Species include the Siamese fighting fish or betta and many species of gourami. A few labyrinth fish, such as the kissing gourami, are egg scatterers. A few others are mouthbrooders. See my paradise fish page for a photo of a 3-month-old paradise fish.
Some species of cichlids and arrowana protect their fertilized eggs by carrying them in their mouths until they hatch. The parent does not eat much during this time.
Eight Possible Breeding Triggers:
1. Changes in water temperature, direction of change dependant on species.
2. Changes in water depth, direction of change dependant on species.
3. Changes in feeding, usually increase in live foods.
4. Changes in tank mates, usually separate and re-join male(s) and female(s) or introduce new fish together.
5. Changes in water quality, usually cleaner water of a pH more closely matching that found in the wild for the species of interest.
6. Changes in lighting, usually increase in day length.
7. Changes in tank decor such as the addition of java moss for egg scatterers or small clay flower pots or PVC pipe for cave egg depositors, etc.
8. A healthy ecosystem in the aquarium or pond including a nice growth of algae (for the fish to spawn on and for microorganisms to grow that will feed the fry).
It may take a combination of the above triggers to initiate spawning.
Some species of fish like corydoras catfish are triggered to breed by large water changes (~50%) with slightly cooler (a few degrees F) water. The actual triggers are the decrease in temperature, decrease in water hardness, and cleaner water. Others like goldfish are triggered mostly by light changes (usually coupled with temperature changes as well). As light increases in the spring, they begin breeding. These species may need their light timers changed with the seasons to breed if kept inside. Other fish like danios and live bearers are triggered almost entirely by an increase in water temperature. Labyrinth fish often are triggered to breed by a decrease in water depth. Most fish require a combination of changes to initiate spawning. Each species is different so it is important to know that species' spawning triggers. Another way to initiate spawning is to feed the fish live foods like brine shrimp, tubifex or black worms, daphnia, etc. This mimics the abundance of live foods in spring and also gives the fish the extra nutrition required to produce vast amounts of eggs and sperm. Feeding fish to induce spawning is called conditioning. Often during conditioning, the male(s) and female(s) are separated. When re-joined, they are often ready to spawn.
Separating parents from eggs and/or newborns:
Except in the case of some species of cichlids where the adults protect the young or in a few other cases of unusual fish, the eggs or newborns and their parents should be separated. This not only prevents the parents and other fish from eating the eggs and/or newborns, but also allows more controlled rearing of the young. If you only desire a few offspring, the eggs and/or newborns can be left with the parents. With many species, a few should survive. With others, like zebra danios, the parents will absolutely eat every last newborn they can reach. Fry can be placed in breeding nets until they are larger if only a few are collected. If many are collected, they should be treated as below under fry care.
There is no one "fool-proof" rule that will allow sexing of any fish. Each species is different. Learn about your specific species of interest. These are just some of the guidelines that one looks for when sexing a fish. Most adult fish in breeding condition can be sexed with some exceptions like certain plecostomus, loaches, etc. In most of those cases, this is because the species have rarely been bred in captivity. For information on sexing fish that I have kept, see the list of species on my fish index.
Size and Shape:
Most fish can be sexed by their size and shape. In some species, females are larger (examples = most danios, most cories, white cloud mountain minnows, most livebearers). In other species, males are larger (examples = many cichlids, rosy red and fathead minnows, rosy barbs). And in some species, the sexes are the same size. Like I said, there is no rule. Prior to spawning, most female fish are noticeably more rotund (fatter). Their ovipositors may enlarge. This is a tube from which the eggs flow at the fish's vent. Males often have a more unusual shape. They may have more adornments or bumps.
Colors and Finnage:
In many species, males are more brilliantly colored and/or have longer fins. Examples include most labyrinth fish (bettas, gouramis, paradise fish), most livebearers (guppies, mollies, platies), rosy barbs, and white cloud mountain minnows. There are a few species where the female is the "better looking." Male livebearers have modified anal fins called gonopodiums which allow them to use internal fertilization of the female. The gonopodiums do not appear until the fish are mature at at least a few months old.
In some species, like goldfish, males develop tubercles (also spelled tubercules) which are white spots or bumps on their gill plates and/or pectoral fins. Sometimes, a female can also have a few tubercles or a male may lack them.
Males often chase females. In a few species, the female is the aggressor. In species where fry receive care, males often become aggressive and/or make spawning sites or nests. This all depends on the species. Sometimes a fish will not behave as its sex would dictate. For example, it is known that two female angelfish may "spawn" and produce infertile eggs. Also, female zebra danios may become aggressive and chase other fish around.
Okay, there is one way to know a fish's sex for sure. If you witness eggs (or babies for livebearers) coming out of a fish's vent, she is female. If you witness milt (sperm), he is male. Oh, but what about hermaphroditic saltwater fish? Okay, so they can produce both! I told you that there is no "fool-proof" method!
Most egg-scatterers prefer to breed on soft locations. The one ideal plant for this is java moss. Other plants like anacharis, cabomba, hornwort, and the roots of floating and terrestrial plants work for other fish like goldfish. Hair algae is also an excellent spawning medium for small egg- scatterers.
There are a number of spawning mops sold commercially. I have bought a stiff plastic-like one for aquarium fish. They never used it. I also bought a huge black hairy one for the pond goldfish. They never used that either. Fish prefer live plants or even the base around pots and fake plants much more than artificial spawning mops in my experience.
You can make your own artificial spawning mop. Get some natural yarn (no dye). (If you can only find colored yarn, boil it first in water at the pH of your aquarium to leach out any color before adding it. Colors will bleed at in differing amounts depending on pH.) Use as much as is appropriate for the size of the fish in question. For small aquarium fish like danios, barbs, tetras, white cloud mountain minnows, etc., you might take about 1/5 of a skein but for large fish like koi and goldfish in a pond, you would use the whole thing. Wrap the center of the yarn with natural twine, another piece of yarn, or fishing line. Then, cut the ends off (all the loops at either end). This gives something akin to a 1000-legged octopus or maybe only 6 legs for small fish. Tie this where it is wanted in the aquarium or pond.
Remember that these natural spawning sites and artificial mops only work if the fish in question is either an egg-scatterer or an egg depositor that likes the item in question. For example, cories are egg depositors but they will stick eggs in java moss and the other mentioned plants and yarn mop readily. A fish like the rosy red minnow which is an egg depositor that only uses hard surfaces is not going to use these sites. Live-beared and mouthbrooded fry will often hide out in the mentioned live plants and yarn as will insect larvae if there are any around. If the plant or mop is floating, labryinth fish may incorporate it into the nest.
One of the common questions from novice breeders is, "Is this clump I have my fishes' eggs or snail eggs or something else?" Another common question is, "I have these fish and which one laid these eggs?" For livebearers and mouthbrooders, this question is not needed since the eggs are kept out of the aquarist's view inside the fish. For egg scatterers, eggs look like tiny clear balls that stick to whatever they landed on, including each other. For labyrinth fish, the eggs are very tiny, clear balls suspended in the bubble nest. With egg depositors, the eggs are usually larger and stuck on some surface. Cory catfish often stick their large eggs on glass and plants, and some species have colored eggs. Look into what the eggs look like for each species in the tank to determine which one laid the eggs. After a day, black spo s should appear at the center of each egg that was fertilized. Later (a few days), you should be able to discern a pair of eyes looking at you if they are indeed fish eggs.
The other possibility is snail eggs or even foreign matter like empty fish feces. For example, sick goldfish often release clear strands with no matter inside when they are ill. Snail and amphibian eggs are usually gelatinous masses. Snail eggs will usually be in clumps on surfaces either in or out of water (depends on species), and amphibian eggs will usually not be stuck to anything but each other or perhaps anchored to a plant. If you still cannot decide what laid the eggs or debris, put them in a small container or tank of water at the same temperature and pH as the main tank or pond and wait. Check daily to see if something is growing in the "eggs." If they are fish eggs, the eyes of the fry inside the egg should be obvious as hatching nears. If after two weeks, nothing has been born, then you will never know if they were good eggs that died, unfertilized eggs, or just some debris. If babies hatch, take care of them as detailed below. Eventually, as they grow, you should figure out what species of animal that you have.
Here are some photos of rosy red minnow eggs to help you decide if you have fish eggs:
Eggs - here is a view of all of the developing eggs. There are lots of eggs. You can see the eye of the developing fish. There are a few white eggs. Those have egg fungus on them. For more information on egg fungus, check out the Eggs - this is a closeup of a few of the developing eggs. You can see the fry's eyes. If you were there, you could see the fry spin around in their eggs!
On 5/8/09, Brett sent these photos of zebra danios eggs and newly-hatched fry.
Zebra danio eggs and fry
Zebra danio eggs and fry - close-up of the previous photo
Zebra danio eggs and fry
Zebra danio eggs and fry - close-up of the last photo; I marked an egg as they are hard to see.
Here are some photos of panda cory eggs from my 20 gallon aquarium:
I took these photos of panda cory eggs on 2/28/09:
Panda cory eggs - 6 on the glass, close-up; day after being laid
Panda cory eggs - 7 on the glass, farther away
Panda cory eggs - in the plastic box; you can see 7 of the 9 eggs that were in there and the few week old panda cory fry on the left
Panda cory eggs on 2/20/10.
I took these photos on 7/3/10 of two newborn panda cory fry that I found in the filter.
Two panda cory fry
Close- up of panda cory fry
Eggs can be removed from the parents tank using a siphon or Python hose into a bucket if they are scattered. If they are attached, whatever they are attached to can be removed. Eggs on glass can be removed using a razor blade, fingernail, or credit card. If the parents were put in a spawning tank and then removed, then the eggs can stay in that tank. Eggs removed from their parents should be kept in a tank with appropriate pH, temperature, hardness, etc. with mild aeration.
To prevent egg fungus, a dilute solution of methylene blue can be added for about a day. The water should be a light to moderate blue. Unfertilized or injured eggs will take on the color of the die. If the die is not used, then those eggs that loose their transparency (often turn white) or appear "hairy" or "fluffy" should be removed. Loose bad eggs can be removed using a glass or plastic pipette while attached bad eggs can be removed using a finger nail or tweezers. If eggs are kept with the parents of some species including some cichlids and fathead minnows, the parent(s) will remove these unfertilized or injured eggs from the nest. If the fungus gets out of control (usually only when methylene blue is not used), all viable (usually clear with small eyes forming; some species like some cories may have colored eggs) eggs should be removed to a fresh setup with water of similar temperature, pH, etc. Newly hatched fry should be removed to separate quarters when egg fungus is present as well, as young fry can die from the egg fungus too. The eggs should be removed to a tank without any methylene blue prior to hatching. Fry do not take well to methylene blue. Usually, keeping the eggs for about one day in the methylene blue solution, removing the colored eggs, and then putting the eggs into a fresh tank where they can hatch without methylene blue works well.
For more information, check out the section on fungus on my health care page.
Filtration, Aeration, and Heating
Most fry can be treated similarly. For the first few weeks, keep them in a 5 or 10 gallon tank. Include a corner filter with carbon and floss inside to provide filtration and aeration. Use pantyhose (see here for more information) to cover the inlet. Alternatively, use a sponge filter or your regular filter with pantyhose over the inlet. If you can include floss or filter material from an active tank, that is good to provide bacteria. Adding liquid bacteria may help start the filter too. Any filter used should be driven by a light flow of air bubbles to provide aeration and break the surface but not beat the fry to death. If eggs are placed in the tank, light aeration is all that is needed until you start feeding. Do not feed until fry are free swimming. Besides the filter with air, you will also need a heater if the room ever goes below about 75 degrees F or you are raising fry that need warmer temperatures. Set the heater to about 75 degrees F for most fry. Some cichlid and other fry like it in the low 80's degrees F. Check to see what temperature your species of fish fry prefers.
For fry-only tanks, I suggest a sponge filter run by lite aeration. For regular tanks that happen to have fry but also have adults, you can put pantyhose or a sponge over the filter intake to keep the babies from being sucked in. It is good to have some filtration to keep the water clean but you also do not want to suck up fry or toss them around like lottery balls.
Water, Lids, and Water Depth
Before you add the fry or eggs, fill the tank either with water from a healthy setup tank or start fresh. If you start fresh to lessen chances of bad organisms from a lively tank, heavily aerate the water for at least a few hours and add about 1 Tablespoons per 5-10 gallons salt (either specifically for freshwater fish or marine salt; do not add lots of salt to tanks of fish that do not like salt such as most catfish), dechlorinator, and anything else you desire like bacteria (Stress-Zyme or related products). Cover the tank with plexiglass or glass to keep moisture in and other pets (if any) out. Catfish and labyrinth fry especially will gulp air. If they are in 75 degree F water and gulp 65 degree F air, they could die. Catfish and labyrinth fish should be in shallow water (under 6 inches) for their first few weeks so they can gulp air easily. Most other fish can have up to a foot or more in depth and survive. Most egg-laid fry swim at the surface anyway.
Lighting and Cleaning
It is also a good idea to add lighting above the tank for a few hours after you add food. Both live foods and fry are attracted to light; thus, the fry find the food easier. Newborn fry are tough. Besides the filter and heater, the tank should be empty. This is so that once you start feeding, you can clean the tank. Use a piece of air line tubing or vacuum tubing to vacuum debris off of the bottom every day or two. How often you do this depends on the number and size of fry and the food you are feeding. Any fry accidentally sucked up can be pipetted or sucked back into the tank.
One fry food is infusuria bought through the mail, cultured from ponds, or made at home with dry formulas you can buy. It is composed mostly of paramecium (a small animal). The old fashioned way to make infusuria is to put some hay in a bottle of water and stick it on the window sill. In a few days or a week, it will turn milky white with microorganisms. You can also just use pond water (which poses a risk of introducing bad animals too like hydra).
A great food for fry is baby brine shrimp. You can buy eggs and hatch them in salt water. Tiny fry cannot eat them until they are a few weeks old while larger fry can eat them right away. Brine Shrimp Direct also sells decapsulated brine shrimp cysts which can be fed to fry without hatching and other products including something called Pearls which is a fry food that is made to move around in the water column to mimic live food.
Other live foods of various sizes include microworms, daphnia, cyclops, euglena, and more. Try to provide other foods as well.
There are a number of prepared foods on the market: Tetramin for egglaying and live born fish, Liquifry by Interpet, and others. One place that sells Liquifry is That Pet Place at 1-888-THATPET. A number of people have come up with homemade foods too, often including strained egg yolk. Judging the amount to feed is extremely difficult to learn and takes trial and error. It is very easy to either starve the fry or kill them with excess food. Once the fry are large enough that you can see their mouths working, you can provide small pieces of the same things that their parents eat. As the fry grow, feed them more, vacuum the tank more, and provide larger tanks as needed. Once the fry are large enough to live with their parents (without being eaten) and eat their food, they are ready to be considered fish.
I feed my fry Liquifry, Tetramin for egglayers, and live baby brine shrimp for the first few months. In February of 2001, I had trouble getting the brine shrimp to hatch in the cold house so half a dozen longfin zebra danio fry were raised almost solely on Liquifry and Tetramin for a few weeks and grew up well. They put on more weight though as I got the brine shrimp to hatch. Month-old fry being fed brine shrimp are obvious with their cute red tummies!
See links below for links to brine shrimp (also called artemia) web pages with more information than you ever wanted to know!
Update 9/24/07: Here are some commercial fry foods that I have been able to buy more recently. My current glowlight danio fry like the artificial rotifers and artificial brine shrimp. Both are very fine.
Drs. Foster & Smith deleted their affiliate program so these links will no longer work. I am leaving up the pictures which are still working for now.
I have moved these to here.
Breeding Tropical Fish - a large good breeding fish web site
JAWS - information from dozens of breeders
Fishbreeding.com - site devoted to breeding fish; I hadn't really looked at it but on 1/28/02, I revisited the site to discover that at least nine of my web pages (those on zebra danios, bluntnose minnows, rosy red and fathead minnows, tank setup, plants and driftwood, pond algae (UV sterilizers), health, fish care (feeding), and chemistry at least) were plagiarized there without my permission or acknowledgment of me in any way (although a few pages do mention my old URL). On some of their pages they claim I gave permission but I never did. Photos, personal references, and links were cropped. It seems most of the site is my information and also some taken from PetsMart without permission. Attempts to contact the webmaster and host were unsuccessful. Please visit my original pages for up-to-date and inclusive information. Update 10/7/02: This site no longer works (yea!) and is on sale for $10,000! (any takers!).
Cathy's Homepage of Tropical Fishkeeping - a full overview of all aspects of breeding
Fish Breeding FAQ
A Fish Breeding Site
Goldfish Fry and Egg Photos
Brine shrimp (also called artemia) links:
Brine Shrimp Direct
Brine Shrimp FAQ - this site no longer exists!
Place to buy live micro-critters (tons of choices for all sizes of fish) for fry and fish to eat:
Also, see the links under the specific fish I list on my Fish Index. There are also links at my Fish Source Page.
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