01-21-2010, 02:19 PM
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First to answer your cycling question, it takes anywhere from 2 to 8 weeks to cycle a new tank. You should have a good test kit for ammonia, nitrite and nitrate; the API liquid test kit is recommended by many of us. It is important that new fish not be added to an un-cycled tank. If you have live plants, they will cycle the tank for you.
I have maintained I don't know how many different species of Corydoras over 20 years, and some have spawned on their own in community aquaria. Currently I have eight species [30 fish] in my 115g and 5 species [28 fish] in my 90g, plus one species of Aspidoras in each (same family, closely related to Corydoras). Most of these are wild caught, a couple are tank raised commercially. This just to let you know of my experience.
Corydoras are especially sensitive to water parameters and water quality. If the aquarium is well established, by which I mean the biological equilibrium is set (usually takes 2-3 months after set-up, all else being good) most species will settle in fine. But they do not appreciate any changes in those parameters or in water quality once settled. Regular weekly partial water changes of 50% of the tank volume are appreciated by corys, along with good vacuuming of the substrate in the area where they feed. I always drop the tablet/pellet foods in the same areas and they will learn this quickly, and be waiting every day at the same time. Those areas I keep free of plants so I can thoroughly clean them; this helps to prevent barbel damage.
They like sand substrates, but fine gravel will work as long as it has no sharp edges; run some through your hand, and if it feels rough, it is probably not suitable. Not only their barbels, but their undersides can be damaged by sharp rocks and substrate materials.
They are shoaling fish, and must be in groups to be healthy. I would not have less than five. In nature they are found in large groups of their own species, and often different species will be together. This shows that while they prefer their own species, they will manage with other species. I have found some species prefer their own more than others, so I try to have a minimum of three of any one species, in tanks with several species. They love plants, spending hours grazing over leaves for bits of food. And they should have some shelter, which can be bits of wood with minimal hiding spots under cover, or just good plant growth. If you look at the photos of my 115g, you will note thick plants with open space along the front. Except during feeding times, when they are all out along the front, they will most often be in amongst the plants. I have a few species that I never see except at feeding times, others are out scurrying over plant leaves continually. But one thing is clear, they appreciate having shelter they can retreat too if they feel the need. It prevents stress, and stress is a major cause of disease and health issues in fish.
They are extremely sensitive to all medications, especially copper-based (as most ich remedies are for example) and salt. On the few occasions that I have been forced into treating one of my display aquaria with any medication, it is always the Corydoras who show, quickly, their stress, and in some cases I have lost otherwise healthy corys simply to medications. I mention this as advance warning should you ever have a situation where treatment may be considered; be mindful of the Corydoras.
Hope this helps a bit. Ask any questions, we're all here to help when we can.