(Originally written for the Tetra Breeder facebook group. Meant to be very basic/introductory.)
Q. Is my tetra pregnant?
Not exactly! Unlike mammals (or some fish), tetras lay eggs. And unlike chickens, most tetra eggs are fertilized when they are laid and not before. If you have an especially round tetra it may well be a female full of eggs, but it will only lay those eggs with the cooperation of a male.
Q. Is my tetra a male or a female?
In almost all tetra species, the primary difference between male and female is body shape. If viewed from above, females will tend to be much rounder than males. In some species, males are also smaller or have brighter colors.
You can often find good information about telling males from females if you search for your fish on https://www.seriouslyfish.com and then scroll down to ‘Sexual Dimorphism.’
Q1. Is my neon tetra a male or a female?
Unfortunately, neon tetras are not the easiest to species to sex. If you have a group of adult neons, the bigger, rounder ones are probably the females.
Q. Can I breed my tetras?
Maybe! It depends on what kind of tetra it is. For lists of easy, moderate, and difficult kinds of tetras, consult the questions below. For most species you will at least need a separate tank, soft water, and some marbles, large-sized gravel, or mesh to protect the eggs.
Most tetras lay their eggs by ‘scattering’ which means they don’t lay the eggs anywhere in particular, and as soon as they finish laying ignore and/or eat them. Protecting eggs from being eaten by their parents or other tankmates is one of the hardest parts of breeding tetras.
Q1. Can I breed my neon tetras?
Possibly. Neon tetras are not the easiest tetra to raise, but many home hobbyists have done it. If you’re willing to make special preparations and don’t mind failing a few times before you succeed then it’s definitely worth trying.
Q. What are some easy kinds of tetras to breed?
Emperor tetras (Nematobrycon palmeri) often leave their eggs and fry alone; if you want to raise tetras in a single-species tank without moving fish around or messing with special water or food, they’re your best bet.
Many species in the Hyphessobrycon, Hemigrammus, and Gymnocorymbus genuses are frequent spawners and have fairly easy-to-raise fry. Good beginner species are ‘black skirt tetras’ (Gymnocorymbus ternetzi), ‘flame tetras’ (Hyphessobrycon flammeus), ‘black neon tetras’ (Hyphessobrycon herbertaxelrodi), or ‘glowlight tetras’ (Hemigrammus erythrozonus). Glowlight tetras even do a cute little barrel-roll when they spawn! You’ll still need a separate spawning tank for any of these though.
Q. What are some tetras that are hard to breed in captivity?
Generally any fish that is wild-caught will be harder to spawn than a farm- or tank-raised fish. Notoriously difficult species include bleeding heart tetras (Hyphessobrycon erythrostigma) and marbled hatchetfish (Carnegiella strigata).
Species in the genus Paracheirodon are often difficult to raise in captivity, but of the three species, neon tetras (Paracheirodon axelrodi) are the ones most often met with success.
Q. I want to try! What are the steps for breeding my tetras?
- Start with a well-fed, healthy, adult tetras. If possible, increase your feeding routine so the fish are eating several times a day.
- If possible separate males and females from each other for a couple of weeks. This isn’t essential but it will help you control when the fish spawn for the first time.
- Prepare a special spawning tank. For almost all species this tank can be quite small; a standard 2.5 gallon/10 liter tank should be adequate. Fill the tank with very soft water (see below) and add a layer of marbles, pebbles, or another covering that will allow eggs to fall through but thwart hungry fish.
- Add a small plant or sprig of moss to the spawning tank. Some tetras spawn in the open water but most like to lay their eggs on or around a plant.
- Ideally the tank should be someplace that is dimly lit but still experiences something resembling ‘dawn’, fading up from total darkness to pale light once a day. Some breeders accomplish this by putting a cardboard box over the tank and then opening a small window in the box each morning.
- Add a pair or small mixed-sex group of tetras to the spawning tank, and wait.
- Every day, check the bottom of the tank with a flashlight for eggs. Healthy eggs are very hard to see, but there will usually be some infertile eggs mixed in which are white and conspicuous.
- As soon as you see eggs, remove all adults from the tank. Then wait some more. Check the eggs once per day, but avoid exposing them to bright light.
- Once the eggs hatch (probably after a day or two), keep waiting. The fry will look very strange, sort of like lazy blobs with little tails attached. This is normal for tetras! Keep checking them daily, but do not feed.
- After several more days the fry will start acting a bit like fish, swimming rather than just flopping around on the bottom of the tank. At this point you can start feeding them tiny, tiny amounts of food.
- This is also a good time to add a filter to the spawning tank and/or start regular water changes. It’s no longer necessary to use soft water, but the water should be very clean and free of chlorine and other additives. Trading water with a different, larger aquarium is a good option.
- If your fry are eating, you’re pretty much home free! Keep them fed, keep their water clean, and move them into larger quarters if it gets crowded.
Q1. Are the steps the same for neon tetras?
The above process will probably work for neon tetras. Neon tetra eggs and fry are especially sensitive to light, so as soon as eggs appear it’s best to keep the tank and fry in the pitch dark in between observations. Once the free are swimming and eating you can provide normal amounts of light.
Neon tetras eggs are also especially sensitive to water quality. Some breeders add peat, leaf litter, or black water extract to the spawning tank in order to provide more acidic conditions which helps the eggs survive.
Q. Where should I get my spawning water from? How do I know if my water is soft enough?
Tetras will often spawn in hard water, but eggs laid in hard water will seldom hatch. If you are seeing eggs but the eggs all turn white in a few hours it is probably because your water is too hard.
Your tap water is almost certainly too hard for most tetra eggs. If you want to check for sure, a TDS (total dissolved solids) meter costs around $20; what you really want to avoid is calcium in your water, but in most cases TDS is a reasonable approximation. If your TDS is less than 100 then your tap water may be adequate.
The safest bet is to start with RO, distilled, or rain water. Don’t worry about buying a home RO system; You only need special water for a few days in a small spawning tank, so a couple of jugs from the grocery store or local fish shop will do the trick. If you live somewhere without a lot of air pollution then rain water is an especially good choice because it’s very soft and also moderately acidic which will help keep your eggs and new fry healthy.
Q. How should I maintain water quality in the spawning tank?
Many breeders use unfiltered, unaerated tanks for spawning. Most likely the adults will only be in the spawning tank for a few days, so no feeding is necessary. Once you start feeding fry you will need to begin small, regular water-changes and/or add a sponge filter.
If your fish lay an especially large number of eggs or many of the eggs are infertile and decomposing, you may need to perform a large water change immediately after the spawn in order to protect the developing eggs. Once the eggs are fertilized the softness of tank water is less critical than other factors like maintaining oxygen and avoiding ammonia.
Q. What should I feed the fry?
At the beginning, don’t feed them! When they first hatch, fry will be in the ‘wriggler’ stage, sticking to surfaces and only swimming in short bursts. During this phase the fry are living off their fat reserves and don’t yet have working mouths or digestive systems.
As the fry start to swim more and sit less (the ‘free swimming’ stage) they will need to eat. Many hobbyists raise tiny live foods to feed the fry, but as long as you’re planning to do water changes you can probably get by with prepared, liquid fry food or finely-ground-up flake food. Even some commercial tetra hatcheries rely exclusively on dry food even for the smallest fry.
If your free-swimming fry won’t eat prepared foods then it’s time to figure out about live food cultures. Vinegar eels are probably the easiest thing to raise; other options are microworms, ‘infusoria’, or baby brine shrimp (for larger fry types).
Q. What if I don’t want to mess with all that but still want baby tetras?
If you’re feeling patient and have space to dedicate to the project, some breeders have had good luck raising certain tetras in permanent, planted tank setups with softer water. A 10- or 20-gallon tank with a whole lot of moss and other fine-leaved plants may provide enough shelter and microfoods for a small number of eggs and fry to survive without intervention.
Here are some species that are known to work in this kind of setup: Emperor tetras (Nematobrycon species), Black neon tetras (Hyphessobrycon herbertaxelrodi), Yellow phantom tetras (Hyphessobrycon roseus).
Another option is to keep a species of tetra that shows parental care, e.g. Copella species. Be warned, though, that although they may tend to their eggs they are not likely to treat their fry as anything other than a potential meal.