How to Breed and Raise Egg-Scattering Fish in Your Aquarium
Breeding aquarium fish is a huge passion of ours, but the difficulty level can really vary depending on their method of reproduction. Some species are easy to procreate because the parents fiercely defend their offspring from would-be predators or the adults give birth to live young that can immediately flee. Other species like rainbowfish and killifish are willing to lay eggs in spawning mops, which are easy to remove and save from being eaten. However, one of the hardest types to breed are the fish that scatter their eggs all over the ground and then happily consume their own offspring right after they are laid. In this article, let’s discuss some tried-and-true methods for breeding egg scatterers, such as tetras, danios, and barbs.
How Egg Scatterers Breed in Nature vs. at Home
Generally speaking, egg scatterers often have a specific spawning season when the conditions are most favorable for their young to survive. The male displays brighter colors (also known as the “breeding dress”) to attract the female and follows her around nonstop until she is ready to mate. He guides her to an ideal spawning site like a clump of aquatic plants, they line up their bodies together, and then the female releases her eggs as the male releases his milt. After resting a while, the male leads the female to another site to spawn more eggs, and they repeat this process until the female no longer has any more eggs to release. Breeding in many different locations increases the chances that some of these hundreds of transparent, fertilized eggs will escape detection as they lay hidden among dense leaves, roots, mulm, and other spawning material.
White cloud mountain minnows are one of the easiest egg scatterers to breed.
Because the eggs are completely unprotected, many species hatch within 24 hours. The clear-colored newborns come with a pair of underdeveloped eyes and a yolk sac that helps feed them for the next 1–3 days until they can freely swim. By day 5, the yolk sac has been absorbed and the hatchlings are capable of hunting for their own food.
While this egg-scattering method of reproduction is quite successful in the wild, it does not work very well in the home aquarium. While most adult fish will naturally breed when food is plentiful, the eggs are quickly eaten because there is less room to hide and scatter them in a glass box. And even if you are able to save the eggs from the adults, the fry are much, much smaller than your typical newborn livebearer, which is capable of eating crushed flakes right away. Instead, you must somehow feed them nearly microscopic foods until the babies are big enough to eat baby brine shrimp and normal fish food. Not to worry though — veteran fishkeepers over the years have figured out how to overcome these obstacles as long as you follow the four keys to success.
4 Steps to Successfully Breeding Egg Scatterers
#1 Get the Right Parents
We need to start our breeding program with at least 1 adult male and 1 adult female that are both sexually mature but not too old to reproduce. For example, South American egg scatterers can often breed as early as 7–12 months old to coincide with the annual floods. Of course, it is hard to determine the age of an aquarium fish, so the safest method is to buy a group of juvenile fish and raise them up until they are of breeding size.
As for sexing the fish, males are usually slimmer, more colorful, and may show sparring behavior. With some species (e.g., rummy-nose tetras, diamond tetras, and green fire tetras), the males have anal fin hooks that help them “velcro” or stick to females during mating, thus increasing the percentage of eggs that get fertilized. While it can be difficult to see the hooks, we’ve noticed in our fish store that these males tend to get stuck in fish nets. On the other hand, females have rounder abdomens (especially when holding eggs) and may be drabber in coloration. If the two sexes look exactly the same to you, then your best bet is getting a school of six fish (or more), which gives you a 98% chance of having at least one of each sex.
Male green fire tetra with anal fin hooks that got stuck in a fish net
#2 Condition the Adults
The whole reproduction process — which includes creating the eggs, performing courtship displays, chasing away would-be rivals, and spawning in multiple spots — takes a lot of energy. Therefore, we need to condition the adult fish for breeding by feeding them lots and lots of proteins, healthy fats, and other nutrients. The surplus of food can also be another signal to the fish that the breeding season has arrived because there is plenty of nourishment available for the baby fish. We highly recommend live foods like baby brine shrimp, blackworms, and even mosquito larvae (which can be collected from a small bucket of water left outside during warmer seasons). The wriggling motion of the live foods helps to entice the hunting instincts of the fish and ensure that they are eating enough.
If you want to increase your production yield, isolate the males and females so that they won’t prematurely mate until you’re ready to collect the fertilized spawn. Heavily feed the two separate groups for at least two weeks so the females have enough time to make a ton of eggs for the big event.
Separating the two sexes before breeding can significantly increase the number of eggs that are laid.
#3 Protect the Eggs
There are many different methods of collecting the eggs and protecting them from the parents, but many breeders use a fry trap or barrier technique because it doesn’t require you to be present at the exact moment of spawning. By installing a grid or mesh barrier, the parents can breed on one side while the eggs fall through the holes to the other side where they can’t be reached.
Set up a specific breeding tank that will eventually be used to raise the babies. The aquarium size depends on the size of the fish you’ll be breeding, but the most common aquarium fish can usually be bred in 10–20 gallons. Remove all snails and shrimp to avoid any chance of the eggs getting eaten, but after the fry have hatched, you can always add them back later to help out as clean-up crew.
For picky breeders, try to get the water parameters (e.g., pH, GH, and KH) to match the fish’s natural habitat during their spawning season. You may need a heater to warm the water to spring and summer temperatures. Also, use a sponge filter or air stone for gentle filtration that won’t accidentally suck up the babies. A mature, seasoned tank full of plants, algae, biofilm, detritus worms, and other microfauna is always helpful because (a) it provides a stable ecosystem that is conducive to raising sensitive fry and (b) it offers extra food sources for the babies to constantly graze on all day long.
There are several ways to build a grid barrier that allows eggs through while keeping the parents out. If the tank is small enough, you can use a large piece of plastic craft mesh or latch hook canvas from a craft store that is big enough to bend in a U shape to cover the entire bottom of the tank and part of the walls if needed, while leaving enough room for the fry to hide underneath the mesh. (Acrylic yarn can be used to sew together two or more pieces of the mesh if they aren’t quite big enough.) For lightweight mesh material that likes to move around, you may need to place the sponge filter on top of the mesh and/or clip the edges of the canvas to the aquarium rim to keep it in place. Place plants like java moss and java fern on the barrier to create suitable spawning sites for the fish, and then the adults are added above the mesh (more on this later).
Protect the eggs by placing a curved piece of craft mesh in the aquarium. In this case, multiple pieces must be sewn together to cover the entire base.
Another easy way to create a barrier is to use a pond plant basket that floats at the top of the tank. Read this article and skip down to the section that describes how to make “Dean’s DIY fry trap.” The concept is the same — after preparing the basket, place the adults and some spawning material like java moss inside the basket. The adults will lay their eggs, which will drop through the holes to the bottom of the tank.
Use a floating pond plant basket to contain the adult fish while their eggs drop through the holes.
Finally, some veteran fishkeepers like to create a more semi-permanent structure that can be used repeatedly for multiple breeding projects. For this DIY barrier stand, you need to get an egg crate panel (i.e., a plastic grid used for ceiling lights that can be found in hardware stores), seine fishing net (with mesh small enough to catch small fish), zip ties or acrylic yarn, PVC pipe, and some cutting tools.
- Use pliers to cut the egg crate panel so that it fits the bottom of the breeding tank.
- Cover the egg crate with a layer of seine fishing net using zip ties or acrylic yarn. If the egg crate panel doesn’t fit the tank walls perfectly, cut the seine net bigger than the egg crate so there is excess netting to roll up and form a squishy bumper along the edges. The bumper fills in any gaps so that the adults won’t be to swim pass the barrier.
- Using 1–2” (2.5–5 cm) diameter PVC pipe, cut out four pieces that are about 3 inches (8 cm) in height. The four pieces of PVC pipe all need to be the same height because they will serve as table legs underneath the panel.
- Place one PVC pipe piece in each of the four corners of the tank, and lay the panel on top. Weigh down the panel with rocks in each corner so that it won’t float.
- Place various kinds of plants on top of the panel, such as java moss (our favorite), anubias, and java fern. Providing different types of leaf textures allows you to see which plants your fish like the most.
Create an egg grate platform covered with seine net that allows the adults to breed above while the eggs fall below.
Now that you have your barrier solution ready, wait for the breeding tank to become well-seasoned and the fattened females to become full of eggs. Place the adults in the aquarium during the evening. If the sexes were previously living in separate quarters, add the females in the morning to let them get used to their surroundings, and then add the males at night.
Check for eggs the next morning. If the majority of the females are thinner and no longer holding eggs, remove all the adults and leave the eggs inside the tank. If most of the girls are still full of eggs, wait until evening to check again. Some species will spawn immediately, while others may take several days, especially if this is their first-time breeding. If you’re having trouble getting them to spawn, you may need to experiment around to see what triggers their breeding behavior and simulates the changing of seasons. Try changing the water hardness, suddenly dropping the temperature using a water change or increasing the heater setting, using a bare bottom setup or different type of substrate, dimming the lights, and so on. Research online to see how other hobbyists have been successful in the past with your particular species.
Unfertilized eggs are usually solid white, whereas fertilized eggs are translucent and tinted with yellow or amber. These tiny, viable eggs can be very difficult to see unless you directly shine a light on them.
#4 Raise the Tiny Fry
The key to successfully raising baby fish is to keep their bellies full and their water clean. Many fry die from starvation, especially since the newborns for egg-scattering fish are often too tiny to eat normal fish foods. Once the adults are removed, some breeders recommend decreasing the water volume so that the fry don’t have to waste energy and swim as far to reach their food. You can lower the water level of the entire tank by doing a water change with a siphon placed inside of a net breeder to prevent eggs and babies from being sucked up. Master breeder Dean likes to place the eggs in a small fry tray that gets constant water changes through a DIY drip system. As the fry grow larger, gradually increase the water level or move the baby fish from the fry tray into a bigger tank.
Master breeder Dean uses DIY fry trays to hold newborn fish so they get constant water changes from a larger aquarium below.
A week before breeding, start preparing tiny foods for the newborn fish. Live foods are highly recommended to catch their attention and entice their appetites, so start feeding them vinegar eels, green water, infusoria, and paramecium. Even mulm squeezed out from filter media and java moss can contain a buffet of tasty microorganisms. Feed them 3–5 times a day and then do daily or multiple water changes per week to keep the water quality high. (For sensitive fry, some breeders recommend only refilling the tank with aged aquarium water.) Once they are big enough to eat baby brine shrimp (around 1–2.5 weeks old), everything becomes much easier. Baby brine shrimp is very high in nutritious fats and proteins and is commonly known as the best way to grow fry big and strong. (See our full article on how to easily hatch brine shrimp for your baby and adult fish alike.) If you have too many fry in the breeding tank and conditions are getting crowded, move them to a bigger aquarium or split them among multiple tanks so that they continue to properly develop. Also, make sure you have an exit plan for where all the offspring will go in the future, such as selling them to your local fish store.
When baby fish eat baby brine shrimp, their bellies turn pinkish-peach in color.
To get started with breeding egg scatterers, we recommend easier species such as white cloud mountain minnows and ember tetras. In contrast, neon tetras are much more difficult and rummy-nose tetras are nearly impossible. While we do not ship live fish, you can look at our list of preferred online fish retailers to see what species they have available and get them delivered to your front door. Good luck with your fish breeding adventures!