sorry to add this, but. ...is it safe to add one, maybe two black ghosts?
Black ghost knife fish are predatory fish so wouldn't be a good idea in a breeding community tank.
You will need to cycle the tank first off, you can find out how to do this this in the pinned articles at the top of the beginners section on this forum- i suggest you do a fishless cycle manually adding ammonia as this way you won't put any fish's health at risk.
You will need test kits for ammonia, nitrates and nitrites(should be available at your local fish store, get the most accurate ones posible), a filter that can easily cope with your tank and a heater preferably set at 24/25degrees for the corys.
Corys prefer fine sand substrate the best as they are bottom dwelling filter feeders, sand also traps alot less waste than gravel does so it is easier to maintain good water quality. You will need to substitute your corys diet with catfish sinking pelets of some sort as well as corys aren't realy designed to eat flakes and do not thrive on them.
Plant the tank with lots broad leaved plants as corys often lay their eggs on these, i wouldn't not advise adding any plecs or other sucking/algae eating fish to the tank as they'll eat the eggs given a chance- taking that into consideration, most fish will eat cory eggs or fry so for successful cory breeding i'd advise you keep the tank a cory only tank.
The easiest corys to breed are albino, bronze and peppered corys- the way to sex corys, is that the females are generally much larger and bulkier than the males because they have to carry large quanititys of eggs, the males on the other hand are smaller and tend to be less bulky looking but more streamlined instead.
Corys need to be kept in groups of at least 4, the more balanced the gender ratios, the more corys you have to each species and the more mature the corys are, the more likely you are to trigger a spawning.
What are the dimensions of your tank i.e width, length and height?
