What is the capacity of the sump? It looks to be around 20 gallons or so which should be able to contain any backflow if it is operating around 2/3 full which it looks like the baffle on the return section appears to be set at. How full are you running it? What size is your display, length and width?
Where are your returns plumbed at? Photos would help.
Where are your returns plumbed at? Photos would help.


