1200mm overflow 2nd drain is super loud

[lonelybones]

Firstly, yes, I know the secondary drain is only supposed to have one air vent, but the hole to the left I plugged with silicone so there is only one vent hole on the secondary…
Specs
Mm 1200gph overflow with 3 3/4in bulkheads and have it setup as dualbean style.
1310gph pump with about ~400gph head loss so 900ish
60g 4ft tank
The problem is if I don’t keep the pump turned down to 12/20 I get sucking noise out the top vent and lots of bubbles from the secondary in the sump(the main siphon is on the reefmat). I don’t mind having to turn the pump down and it work properly but I bet it’s only at about 5 to 600gph turned down that much and would be nice if I could get my full use out of my overflow yes I know I need a bigger pump to reach its max but I can’t even run it at 900gph without lots of secondary noise and it should be able to handle that fine…appreciate the knowledge!!

 

[lonelybones]

I’m going to post this to general discussion for more eyes…don’t know how to delete my bad