Small, attractive and immoderately charming, the Pygmy Corydoras is a fantastic aquarium fish. With its relative ease of care and intriguing behaviour, Corydoras pygmaeus makes an interesting breeding project for both the relatively inexperienced and consummate expert alike.
At only 3cm or so, the Pygmy Cory is one of the smallest aquarium fish, requiring relatively little space; A 10-gallon aquarium could happily house a decent-sized shoal. In the wild, they are found in the Rio Madeira basin in small ponds a creeks characterised by marginal vegetation and leafy substrates.
The perfect setup
Whilst tolerating a manageable range of water conditions (pH: 6.4 to 7.4; Temperature: 22 to 26°C; Hardness: 2 to 15°) Corydoras pygmaeus prefers a dimly lit tank with roots, leaves and vegetation galore. A High-energy aquascape with lighting that appears to be plugged directly into a nuclear generator will result in skittish behaviour and dim colouration; the dimmer your tank, the brighter your fish.
An Amazon-style biotope would be a great environment for this species: add plenty of natural décor such as driftwood, bogwood and leaf litter as well as a few floating plants and you can have yourself a natural-looking tank in moments. A substrate of fine sand is always preferable to gravel or even some of the larger aquascaping substrates as these have a propensity to damage their barbels.
If you’re worried about staining your water so dark that you can barely see the fish, try adding some activated carbon to your filter: it should gradually reduce the amount of tannins in the water and help your tank return to a more golden colour. The acids also released by this type of décor are actually beneficial to your fish as well as representative of their natural environment.
It’s small size means that tankmates should not be significantly larger fish. Anything larger than an Apistogramma should be kept away with smaller characins making much better tankmates.
Any food offered should be small enough for them to eat or crushed up so that it is. Live and frozen food is ideal for bringing them into breeding condition.
Sexing Pygmy Corydoras
It’s very easy to sex this fish: females are much larger than males with rounded ventral fins. Males are smaller and have a more pointed set of ventral fins. Females will also appear much wider than males when viewed from above.
There are a variety of strategies that you could adopt, and there’s no real need to separate the fish into breeding tanks, however this will yield the greatest number of fry. Either way, you should typically have more males than females in a group, possibly with a ratio of 2:1.
Is will be quite apparent when your fish are ready to spawn as females will appear fuller and will attract the attention of males who will chase them around the tank. At this stage, it is a good idea to perform a large water change using water of identical parameters only cooler than your tank water in order to replicate the rainy season. This, in conjunction with increasing oxygen levels in your tank is likely to induce spawning.
You will notice an increase in activity with males chasing females and eventually spawning. This is achieved in the T position until an egg is fertilised. At this point, the female will deposit the egg on either the aquarium glass or even amongst the leaves of any plants in the tank. This is often ideal as leaves can be snipped off and the eggs transferred into a raising tank with minimal disturbance.
Hatching and raising fry
Unless you want to see them eaten, you must separate the eggs from the parents as they will eat their own or each other’s eggs. The hatching and raising tank should be as close as possible a match for the water parameters of the main tank and ideally be filtered with a sponge filter.
It is possible to remove eggs stuck to the aquarium glass by simply rolling them onto your finger. They should be both strong and sticky enough to survive this technique. The addition of some methylene blue will help to prevent fungus although a cherry shrimp or two will do an excellent job of removing fungus from your eggs. You should expect the eggs to hatch within three to five days.
After they have consumed their yolk sac, you will need to provide some infusoria for them. This should be prepared in advance or achieved with the addition of a nicely decomposing catappa leaf or two in the raising tank.
In addition to infusoria, you will be able to start feeding them with microworms after a week or two.