If its; the pump pumping too much then a ball valve is a nice cheap solution, less than $10 at home depot.
If you wanted to you could buy a new overflow or pump but then youre looking at more money for sure.
Get the stats on both or the brand and model and we can go from there.
180g Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40b REEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.