4 Airstones Inside a 75 Gallon Resvor? Not Enough?

Was wondering if i might need couple more any thoughts?

your gonna need to measure the out put of your air pump to find out how much air pressure you need. I reccomend 1.5 liter per gallon. But some use less. Youll want at least one liter per gallon of air pressure.

Then to decide how many stones you need it will depend on the shape of your reservoir. If you running a food grade barrel you can get away with 2 large airstones as long as your pressure rquirement has been met. If you in a panda you'll want more and smaller airstones to cover the area of the basin. 6 medium on an commercial air pump should do it. If you want it to thrive I would reccomend a Commercial Air 7 to meet your air requirements.

If you are looking for info on air and air stones this might help a bit --> https://www.rollitup.org/hydroponics-aeroponics/428990-oxygenation-air-pumps-nutrient-uptake.html

Not sure if it will help or not, but you never know.

Thanks to both of you that will be very helpfull information. +rep to both

The simple answer is to have at least one watt of air power per gallon of water, otherwise you need a meter to read your DO level. I have a Eco air 5 pump (80 watts) and 70 gallons of water between three reservoirs. My biggest (40 gallon res) has five 12" stones.