Welcome

In planted tanks it is possible to add fish almost immediately after setup with no ammonia or nitrite spikes. And all the fish live. But to be safe what I do is let the live plants condition the tank for a week then add a very small amount of fish and don't add food for a week. Then do a more normal amount of fish and start very light feeding.

But still if you had sufficient fast growing plants like anacharis it is possible for the fish to experience no stress even if they are added almost at startup.

On the question of the air pump, if the pump is above the tank they is no need for a check valve. In fact I don't trust check valves and always put the air pump above the tank.

But then I haven't used an air pump in over 20 years. And no mechanical filters since the late 70's.

Just my .02

And welcome.

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fw leiden since 1979, fo salt since 1979, mixed reef 55g 2002-2009. Strong emphasis on the tank taking care of itself. Balanced with plant life, no water changes, tap water, no filters in FW. Only dosing calcium, alk, mag in marine reef tanks. http://www.aquariumforum.com/f15/my-...ods-26410.html
recent tanks (till 2009) 7 years- 10g FW leiden 7 yrs, 55g mixed reef 7, 2 yrs, 20g FW leiden, 10 g fw leiden , 29g mixed reef, current tank 55g leiden