plumbing help for 120 bean animal

i have a 120 gallon tank with 4 holes drilled in the bottom with a center over flow. i have a open stand pipe for the main drain and then a durso for the secondary and then an open emergency. i drilled a hole in the cap of the durso like everyone says on YouTube and put a air valve in the hole but no matter how much i open the valve the durso fills and drains over and over again, if i take the air valve off completely it stays pretty constant but makes a lot of noise. i also am getting a lot of bubbles in the sump from that drain, i tried putting some airline tubing into the hole and leaving it open but it just makes the durso fill and drain like if i had the valve on there .

also the over flow it self makes alot of noise just filling up, as in the water flowing from the tank into the overflow any idea how i can reduce the noise on that also?

some one please help i need to get this fixed!

does the air valve need to be a one way valve?

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