Lights shouldn't run more than 8 hours a day. Past 8 you can run into algae problems.
As BB multiply they work to take out ammonia first, you dose ammonia(Fishless cycle) or you have some stock(fish in cycle) to make the ammonia. Next, they will tackle nitrite, both ammonia and nitrite over time will try to skyrocket in level. This is part of the process and why in fish in cycling you do a lot of water changes. Once your BB can clear high levels of ammonia and nitrite in 24 hours with only a byproduct of nitrate, your tank is cycled.
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