Before anyone asks, no, I am not attempting to breed any bettas right now, or any time soon. I've just been researching the subject as I play around with the thought of attempting to single out the gene-type that causes the strangely elongated pectoral fins, in case I ever do decide to try it in the future, as I'd like to try and get it right the first time.
If I were to use a 20gal long tank for the breeding/spawn tank, which would then become the housing for the young fry (parents obviously removed) until they start becoming mature enough to determine male vs female (which from my readings is between two and 3 1/2 months?) and get separated to their own bowls, would it be better for the fry if the tank was cycled, or not cycled? Would it be easier to keep a cycled tank or non-cycled one when we're dealing with betta-fry? How quickly are several hundred fry going to dirty up a tank of that size and require a water change, both cycled and non-cycled?
Also, while the males would obviously be getting pulled out once I can determine their gender, how many of the females would it be safe to leave together in the 20 gallon as they mature past three months of age? Does the fact that the females would be siblings make any difference at all on their aggressive nature? Anyone have any knowledge from betta breeding experience they can impart upon me?