Water & Air Pumps

I'm growing in soil but have a couple water reservoirs that I'd like to keep oxygenated and mix nutrients with, I've been told that adding air to the water has a lot of benefits like removing chlorine and other unwanted solvents and impurities. I also heard it'd be beneficial to add a water pump to mix nutrients and keep the water circling. Just wondering if anyone knows what size of air and water pumps would be ideal for a 25 gallon reservoir (6.6L) and also a 105 gallon reservoir (400L).

Thanks!

The pH will fluctuate with the aerator, just keep an eye it.