Jamo, how small of a nano are we talking?
I hear you. I've kept tanks since the late 1970s. High water circulation alone will provide extra oxygenation due to the agitation at the surface.
Erin, like suggested, until you have established a proper nitrogen cycle in your tank, you've got to do water changes to bring the ammonia level down.
Hey Erin. No I have not used Purigen. I don't even run activated carbon in my tanks. I'm pretty sure Purigen doesn't need to be regenerated prior