Want to take your skill as an aquarist to the next level? Or maybe you've seen your fish spawn in your tank and are wondering if you can raise the babies? You're in luck! Many small, egg-scattering schooling fish can be bred in the home aquarium. Some are more difficult to raise than others, but whether you succeed or not, breeding fish is a fascinating and rewarding experience.
Below, let's take a look at what goes into breeding egg-scattering schooling fish like tetras, danios, and rainbowfish. With some luck, you'll soon have more baby fish than you know what to do with!
"Egg scatterer" (a term mostly used by hobbyists, though it also pops up in some scientific literature) refers to a wide range of small freshwater fish that reproduce in more or less the same manner. Instead of building a bubble nest (labyrinth fish), using a well-defended cave or tube (many catfish and cichlids), or broadcast spawning in massive reproductive events (large saltwater fish), egg scatterers lay large amounts of eggs at once and rely on the environment to protect their offspring.
As we'll see, the egg scatterers can be roughly divided into two categories, the floor layers and the mop layers. The former simply lets their eggs drop straight to the substrate, while the latter at least makes the effort of finding some plants to lay them in. Other than that, though, the approach is roughly the same for all egg-scattering species:
As with most other fish, the eggs hatch in 1–3 days (depending on temperature). They don't pass through a true larval state like in many saltwater species, though the fry do spend their first three days or so mostly immobile and feeding off their yolk sacs. Once the sac is finished, they need to find their own food — usually starting with tiny zooplankton, like rotifers.
The good news? Although some species are more difficult to breed and raise than others, this entire process can be replicated in the aquarium. There's just one caveat: you need to set up a separate spawning/breeding tank for the best results.
In short: because egg-scattering fish aren't used to being in the same room as the eggs they just laid, and will simply eat them. If they don't, their tankmates probably will. And if the tankmates don't, then the babies will likely get sucked into the filter as soon as they hatch — display aquariums are surprisingly dangerous places for newborn fish! Also, even the most "alive" tanks might not contain enough zooplankton to sustain entire batches of hungry babies.
True, in lush, densely planted tanks you might find your schools of tetras, minnows and the like mysteriously expanding over time. If the eggs and fry go unnoticed for long enough, some of them do manage to survive into adulthood. But if you want some control and to actually have a shot at raising dozens of baby fish at once, a separate tank for spawning and rearing (or one for spawning and one for rearing, if you have mop layers) can come in mighty handy.
Don't think this means you have to go through the whole annoying process of setting up an aquarium and waiting for it to cycle again just so your fish can get laid. Most fish breeders instead rely on daily water changes — which are necessary anyway to remove uneaten food and other debris — or insta-cycling their spawning tanks with material from an existing aquarium. Some don't use a filter at all. We'll look at how to very easily set up a spawning tank for egg-scattering fish in a minute, but first, let's meet our protagonists!
Tip: Because you have to rear the fry yourself for the best results, breeding egg-scattering fish is always a labor-intensive process. If you're looking for a quick way to make a buck, this probably isn't it — any proceeds are unlikely to cover the hours spent raising the baby fish to sellable age.
A lot of them! If you're looking to try your hand at breeding an egg-scattering fish species, you probably don't have to look further than your existing community tank. As we've seen, there are two main categories of egg scatterers. The floor layers take the "scattering" concept very seriously. The mop layers, on the other hand, at least maintain some semblance of organization by laying on plants or special spawning mops.
The concept of the spawning tank was pretty much invented for these guys. They'll go through the entire process of displaying, courting, and spawning, only to turn around and immediately eat their offspring! Because the eggs are laid all over the tank floor, there isn't much you can do if this happens in the display tank.
In a spawning tank, on the other hand, you can easily install a slotted material on the bottom. The eggs fall through to safety, keeping them out of the parents' reach until you can return them to their regular home.
As mentioned, mop layers work a little differently. For starters, they can take weeks, not just overnight or a day or two, to lay all their eggs. Secondly, instead of the eggs ending up all over the tank floor, they specifically search for fine-leaved plants to lay them in. They'll also lay on soft cloth mops provided by the aquarist, which makes separating the offspring from the hungry parents a breeze.
Some aquarists hang the mop in the display tank so they only have to set up a separate rearing tank, while others like to have both a spawning and rearing tank for more control over the process. You can start by trying the rearing tank-only option — just set up a spawning container later if the mops get raided in the display tank.
In our experience, white cloud mountain minnows in particular are a breeze to breed, as are zebra danios and ricefish . You can also try the lovely cherry barb or ember tetra if this is your first time raising baby fish. The rest are doable, too, but their fry may be more finicky or they come with specific water parameter requirements.
Some fish simply refuse to get it on in the aquarium at all unless the conditions are just right — lookin' at you, cardinal tetras. Of course, we encourage you to give it a shot anyway!
Let's start your fish breeding adventure. The first step is to set up a spawning (floor layers) or rearing tank (mop layers) for the egg-scattering species of your choice. It can be about half the water volume the fish normally need, which comes down to about 10 gallons for most of the egg scatterers mentioned above.
You technically don't have to use a real aquarium (a food-safe tub works), but given how cheap a basic 10-gal rectangle is, most aquarists do. Just make sure the tank isn't very tall, or alternatively don't fill it up all the way. In the wild, after all, most of these fish hatch in the shallows where predators can't reach them. The babies aren't used to having to swim a lot to find their meals.
Technically , you don't need a filter for the breeding tank either (you'll be doing daily water changes anyway), though most aquarists nowadays agree a gentle sponge filter is helpful. If you've got time, you can even run the filter in the main tank for a few weeks to populate it with beneficial cycling bacteria. This can help to keep the water parameters stable, but is not a must.
What you definitely do need are a heater, airline tubing for water changes, and water from the display aquarium.
You will need something for the eggs to fall into so the parents can't reach them. This can be anything from a plastic mesh grid placed an inch or so above the bottom of the tank to a big mass of Java moss, or even just a layer of marbles.
You'll move eggs stuck to a spawning mop into the tank, not the parent fish, so there's no need for extra protection. Just fill up the tank, turn on the equipment, and you're all done for now.
Have you bought the fish you'd like to try your hand at breeding yet? If you haven't, see if you can find specimens that are still quite small themselves. Most can reproduce at less than a year old, with younger parents being more productive than older ones. Because you usually can't distinguish between the males and females at this age, it's a good idea to get a group of 8+ so you always end up with a few of each.
Some aquarists like to separate their new fish until breeding time has come, which helps prevent them from accidentally getting it on prematurely. This is a hassle in a general community aquarium, though — no way to easily pop in a divider, and small breeder boxes can stress them out (plus, it can be difficult to even tell which fish are male and which are female when they're not in breeding mode yet). You can always keep everyone together for the first round and see if it works out, optionally going for a more serious set-up later if you find you're enjoying life as a fish breeder.
Once the future parents are all settled into their new home, it's time to start working on conditioning them. Breeding is a tiresome activity for a little fish, especially the ones that need to produce dozens of eggs. Your main goal will be to fatten them up with an abundance of healthy live foods ( Daphnia , brine shrimp) rich in proteins and fats. This also helps simulate the start of the rainy season, when egg scatterers tend to breed: in the wild, the arrival of rain means a flood of all sorts of tasty larvae.
You'll know your fish are ready to reproduce when the females stay noticeably fat even if they haven't eaten in a while. The males will start coloring up and acting like little scaled peacocks.
Tip: Most male egg scatterers sport tiny hooks on their anal fins, which help them cling to the female during the spawning process. If you're not sure if a fish is male or female but it gets stuck to the net when you catch it, you've got your answer right there.
If you're using both a breeding and a rearing tank, move a courting pair into the breeding container (female in the morning, male in the evening) with a spawning mop. If you only have a rearing tank, just put the mop in your display aquarium. Watch it like a hawk, especially in the early mornings when most fish prefer to spawn.
Once eggs have been laid, move the mop to the rearing tank to keep the babies safe from their parents and hungry tankmates. Then optionally introduce another mop — though keep in mind more baby fish does mean more work for you!
Move a courting pair into the breeding tank (again, female in the morning, male in the evening; she needs some time to settle in without being chased all over the place). Play some Barry White overnight and you might find the female looking much skinnier in the morning!
Once the female has laid her eggs, that's it — unlike with mop layers, which can keep going for days or even weeks, she won't produce more for now. You can focus on raising this batch of babies, which will hatch soon, and then optionally try again with the same or another pair.
Tip: If your fish are flirting but nothing's really happening, they may need some extra motivation. Performing a large (~30%) water change with slightly cooler (2–3°F) water, simulating a rainstorm, might just do the trick.
Your fish breeding starter pack:
Got eggs? Congrats! Your grandfish will start hatching in 48 hours or so. If their rearing tank (or spawning tank that is now a rearing tank) has a light, it's best to keep that turned off until the fry are five days or so old. Be sure to close the curtains as well if the room is bright; baby fish are very sensitive to light.
The only exception to the lighting rule is a regular fungus inspection: every morning and evening, briefly use a torch to check whether any eggs have gone hairy. If so, you can carefully remove them with tweezers to prevent the fungus from spreading to their healthy brothers and sisters. Some aquarists also like to add a few drops of methylene blue (an antifungal) as soon as the parents have evacuated the premises, but this is not a must.
Once the eggs have hatched, the babies' single biggest threat is starvation. As we've mentioned, they live off their yolk sacs for the first three days or so and won't need feeding yet. They mostly lay around during this time and don't move much. Your baby fish food supply should be ready to go, though, because they'll develop a taste for microorganisms like infusoria, paramecium, vinegar eels, and the like as soon as they start swimming. Green water, which contains a wide variety of microscopic bugs, is an excellent source of food for them.
You can culture all these fry foods yourself at home, though you'll need a starter culture for some of them. Just pick whichever option sounds the most doable! All should be loosely covered with a paper towel and rubber band, not a lid:
Once your baby fish are swimming freely and there is no yellow bag (yolk sac) visible, you can use a pipette to squirt a tasty buffet near them 3–5 times a day. Use some airline tubing to siphon off leftover food, poop, and any dead fry (it happens, sorry!) every day, or even twice a day as the growing babies start eating more.
Tip: Something gone wrong with your microorganism of choice? This batch of fry might not be lost just yet. It's not ideal, but try squeezing some water from a cycled filter (or even a bunch of Java moss) straight into the rearing tank during mealtime. The sponge is full of the tiny critters that baby fish love to eat, though this method means you'll be doing a LOT of siphoning to keep the tank clean.
Once your baby fish reach the ten-day mark, it's time to start cookin' up some super-nutritious baby brine shrimp. Only tiny freshly hatched shrimp will serve for now — the bigger leftovers can go to the parent fish — so be sure not to hatch all the eggs at once. We've found that hatching a small new batch every other day ensures the baby fish always have something to eat.
When the first batch hatches, place a few of the brine shrimp nauplii in the rearing tank to see if the fry are big enough to eat them yet. If they are, you can start phasing out the infusoria or whatever you were using; if they're not, just start some new eggs and try again when those hatch. You can gradually feed bigger and bigger baby brine shrimp, eventually gradually switching to crushed "grown-up foods".
You can consider your baby fish in the clear once they reach the stage where they reliably eat crushed flakes and other commercial formulations. They'll also have colored up a little at this point, looking like perfect little copies of their parents. Congratulations: you did it! You bred fish! See you for the next batch — you're probably hooked at this point.
We've mentioned a bunch of different products in this guide. In case you've lost track, here's a handy fish breeding shopping list to take to the LFS or base your online order on:
Let's be perfectly honest here: everyone loses some batches of baby fish, especially during their first few attempts. We have. It's heartbreaking, but remember they would hardly have stood a better chance in the wild! Your fish will breed again, and you'll soon get the hang of it and develop your own techniques. After a while, you'll find you can consistently raise at least a few babies per batch to adulthood, and that's awesome.
It all sounds very easy when you read this guide, but newly hatched fish are genuinely challenging to care for. They're fragile, starve easily, and sometimes just fail to thrive despite everything going as planned. Give yourself a pat on the back once your first "homegrown" fish reach the two-month mark, and don't forget to share your success in the comments below.
Godinho, A. L., Lamas, I. R., & Godinho, H. P. (2010). Reproductive ecology of Brazilian freshwater fishes. Environmental Biology of Fishes , 87 (2), 143-162.
Nunn, A. D., Tewson, L. H., & Cowx, I. G. (2012). The foraging ecology of larval and juvenile fishes. Reviews in Fish Biology and Fisheries , 22 (2), 377-408.