water flow

Hi There I have a 20 litre nano tank which came with an Aqua One Air Pump, as the tank has a built in filter compartment at the back. Now, previously I had a Betta fish in this tank and even though I had the pump on the lowest setting, it was truly blasting out. I DIY'ed a solution by...

I have 2 power heads in my tank. Just wondering where the best placement is please? Opposite each other? Next to or away from filter outlet?