Behavior is normal for danios. They are like little race cars and love playing chase. In a cycling tank, water changes are the most important thing. Keep a close watch on ammonia levels as ammonia is toxic to fish. look for an ammonia spike over the next several weeks, this is a sign that your tank is beginning to cycle. Try not to add chemicals, but do water changes instead. The addition of an airstone will be most beneficial as O2
levels drop with increasing NH3
/4 levels. Keep a journal of your water changes and water perameters and it will be obvious where the problems are. 90% of new aquarium problems can be remedied with water changes. look at small daily water changes, and a 50% water change once every other week.