Breeding Medakas

There is literally not much to it, if you feed them enough, give them decent water conditions, a few hours (10+ but 14 is ideal) of light and water temps over 18c they’ll probably start laying eggs.

They will lay eggs everywhere, over plants (plastic/real) filters, air tubes, ornaments, whatever. The trick isn’t to make them breed, the trick is getting the eggs in large numbers, without getting somewhat tainted, eaten, fungus or damaged and then raising those eggs.

In a well planted tank, finding eggs will be annoying, they’ll lay on everything. While some might want to raise the fry in the same container as the parents by providing a haven for them to hide in, a better way to stop them being predated by the parent or other occupants of the container is to seperate the eggs into a container to be hatched somewhere on thier own. Which means you need to collect the eggs in an efficient and easy manner.

If you remove all the easy to rub against objects in the container and only leave one easy to remove mop then ideally you get all the eggs on the mop and none of the inconvience of having to find eggs and collect them. Traditionally some breeders remove the eggs from mops and roll them to clean them. I havent found this to be neccesary, while you lose a few eggs to fungus from general contamination, its vastly easier to just remove the mop and put it into another container for 7-14 days until all the eggs hatch and them remove the mop. If I was worried about fungus I’d probably just add meth blue, but honestly there aren’t enough lost to fungus to bother.

I tried a few mop types and designs before I settled. Acrylic yarn ones, made picking left over eggs off annoying and the mops often trapped young fry in them when being removed, the loop style scour pads and palm and coconut fibre ones were annoying to get eggs out of the middle. The superior ones are the basic ones most breeders use which are the scour pad finger ones. Theyre easy to pick eggs off if you need to, they sit in water containers easy, easy to make and move.

I put the mops into smaller containers with daphnia and 3 times a day I feed them with a long squirt of green water from my green water buckets, a splash of water from my infurosia tank and a few teaspoons of whatever 80-200micron powder food amounts depending on how many babies are in the container.

Depending on how many mature females you have the amount of eggs may produce a lot of hatched fry, depending on the size of your hatching containers, you may end up with many fry. The fry will fight and spar at a very young age, the most important factor if that even from a young age the fry produce certain chemicals which will stunt growth, so once fry gets to a certain density, you need to upgrade the vessel to make sure they continue to put on weight and size. The reason for the small container at hatch stage is that you want a large surface area (for surface skimming) so the food doesn’t get lost in the large volume of water. I use 3 litre containers for hatch size, to make sure all the food is nearby and of easy access.

The hard stage is from hatch to 2mm, the babies are small and the mouth size is only 80-150micron in size and providing food at this size is hard. A lot of the powered food is too big at this stage and to be honest I’m not quite sure how much powered food, green water and daphnia is effective at this stage, but keep an eye on the stomachs of your fry at this size to ensure *something* is getting into thier stomachs. I’m pretty sure only infurosia and bacteria is eaten at this stage, produced possibly from snails eating the non eaten powdered food, but the green water keeps the daphnia pumping out eggs/babies, the snails eating left over waste, producing bacteria and waste at least until they can eat baby daphnia and powdered food. I keep them in clear containers so its easier to see how large the stomachs are growing.

Once the babies are about 2mm with big plump stomachs theyre much much hardier, they’ll increase size and weight much faster once they can get the powdered fry food into thier mouths, at 2mm I normally move them into 25litre tubs and let them eat as much powdered food as they’ll take. Medaka are very slow growing compared to other fish I have raised. But they will grow. A high protein diet is essential for bulk weight after this size. Culturing and feeding live food will probably increase size as well, but the scale at which I can raise infurosia and daphnia at the required sizes mean most of the stock goes into smaller fry tanks and adult tanks. The intermediate size the daphnia are either too big or are instantly consumed or the infurosia are too small for the growing fry at this size.

It will take a few months but they will get to 1-2cm as long as the container is large enough. Once they get to 1cm they can probably move to 0.2-0.5mm adult food. The adult food is a much better for them then persisting with the powdered food. The dust type foods are generally have very few ingredients and not that comprehensive as a diet. You may have a time when tubs need both powdered and adult food as babies grow at largely different rates, many fry might not be big enough for adult food, also adult food (when grinded etc) are not all uniform in pellet size, so an exclusive adult food would starve out some fry.

As they grow, larger tub sizes will help growth and muscle tone, try and give a comprehensive food to help colour and condition as the fry grow. Certain foods help increase colour and condition, a good greens, insect and fish protein diet will help with this.

Good luck.