A typical breeding setup for Corydoras.
When one is trying to breed Corydoras, a special breeding tank will usually give you better results than waiting for them to spawn in the community tank. Even if they do spawn in the community tank, it is very likely you will not notice it at all. The eggs are well hidden by the fish, but even if the eggs survive the hungry attentions of the co-inhabitants of the tank, and the parents themselves, the larvae coming out of the egg are extremely vulnerable. The first thing they have to do when emerging from the egg is to go up for air to fill the swimbladder. Still, some may occasionally survive this, and after a month or three the owner will be in for a surprise when the first 2 cm long juvenile calmly cruises the tank for food.
Since you selected this page let's assume you plan to breed a particular species of Corydoras. For the species specific information please go to the fish description part of this website. The general tank setup will be described below.
The following information is not a must, but things that have worked for me, or which I've read. By no means expect your fish to start breeding immediately after you've invested a lot of money to copy the described tanks, materials and possibly fish.
1: The Tank
A typical corydoras breeding tank should be long enough. As a rule of thumb length of the tank should be at least ten times the maximum size of the adult fish. There have been numerous reports about full grown paleatus spawning in a 30cm tank or even smaller, but ofcourse no-one reports the failures. Take it from me that the bigger the tank is, the higher the succes rate.
Depth of the tank, the deeper the tank, the better. Minimal depth of the tank would be equal to the height.
Height of the tank should not exceed 30 cm. ( The tank could be higher, but then simply do not fill it up over this height.
2: The Fish
This is one of the most important issues, although it's hardly ever mentioned in any setup information. Ofcourse the fish have to be healthy. And yes they should be fed well. But that is about all there is to find. First things first. A group of fish should be selected. Furthermore, they should be mature enough. The best way to get this is ofcourse to buy full grown wild caught fish. If you do buy wildcaught fish, the first thing to do is to get them disease free. Some medications used on fish will render them temporarily infertile, one of the reasons why so many first spawns go bad.(Although some people theoretisize this to be a learning proces for the fish, nicely thought of by humans, but in free laying species there is no feedback to the parents that the eggs are not fertilised, so how could they learn?) During transportation usually the fish are treated really bad. Large fish(the ones we want) are usually more expensive because of the higher death rate during shipping(Lower water to bodyweight ratio) and because the shop owners know. Do not believe shopowners, they will try to get as much profit from sales as possible. Prices tend to skyrocket for the people they know will buy this or that new or rare cory. Send your friends, and jeez, half price for them. Basically it's what the fool will give. they will charge. Do not under any circumstance buy only three fish, because they are expensive, and another three in a months time. There is no guarantee it will be the same species, or type locality. Small fish will also grow big, although for most species it takes a minimal of two to three years to reach a reasonable size, and growth rate is reduced in tanks if compared to nature(ref article?)
3: The Interior
If you'd like a nice looking tank, you are not going to like this part. Don't worry, the fish tend also to breed in those as well. Soil should be sand, approx. 0.5-1cm layer. Hiding places, one will suffice. Coconut shell, or better is to create a cave with multiple exits by placing a flat stone on some smaller stones. Plants are optional, but not neccesary.
4: The Light
Twelve to 13 hours of light, preferably subdued light, or no light at all, if the tank is near a window.
5: The Substrates
6: The Filtration
Strong filtration, especially in one area of the tank. There should be areas where there is little or no current, so the fish can rest
7: The Temperature
Daily 50% waterchanges with pretreated water, approximately 5-10 degrees colder than the water in the tank. Be carefull when changing the water, if a part of the glass is directly exposed to 10 degrees colder water, it may break!
Feed the fish well, as much as they like and more(Your doing daily waterchanges, so any left overs are no problem). Feed them with red mosquito larvae(bloodworms), Daphnia, Artemia, Chopped eartworm and tubifex.
If you keep this up for a week or two(or longer) most Corydoras will spawn. Some require more attention, and should be kept in soft, acidic water for a while. Then change the water with soft, neutral water, to get both a rise in pH and a drop in temperature.
Be very carefull when handling the eggs. The best thing to use is spawning mops, which will enable you to remove the eggs from the tank, withoit handling them. Place the eggs in the same water as is present in the spawning tank in a small breeding tank. Still, many eggs may fungus, and most of the times the fish have a mind of their own where the eggs should be placed. If you have to remove the eggs by hand, wash your hands thoroughly before removing the eggs(make sure no soap remains on your fingers). Some people use a razorblade to remove eggs from the glass, but I've never been able to do that right. Corydoras eggs are extremely hard, and you cannot squash them by handling them.
Back to the eggs fungusing. Eggs fungus as a result of bacterial attacks, which results in the shells damaging. The fungus is the second infection, because it attacks damaged eggs. Most of the times that I tried to raise the eggs in a separate raising tank, 60-80% of the eggs fungused. Adding a preventive medicine like methylen blue helped a bit to increase hatch rates. After that I started using breeding nets, which hung from the side of the tank in the spawning tank. Here hatch rates remained around 90-95%. I used to keep the fry there, feeding them artemia, for a week or two, and then I transferred them to a raising tank.Using a pure glass bottom in a raising tank may seem a good thing to do, since it's easy to clean. But it resulted in my case often in the fry developing fungus. On a glass bottom tank, a thin layer of bacteria will be always present, which may have caused this. After i added a thin layer of sand, the fish stopped developing fungus.
It's a really nice sight, having an 80 cm tank filled with over a 100 juvenile Corydoras(in my case panda). You can observe some natural schooling behaviour, and watch them eat and grow. They can grow quite fast, up to 2-3 cm(depends on the species), but after that growth comes to a halt, and it may take up to a year before the fry are the same size as the juveniles you mostly see in the shop. It will take at least a year more for them to become fully grown.
If you have any comments please mail to aquaworld
All images, information, text, and other information/items in this site © Aquaworld website as described in the Berne convention.