The best is to replace, in the short term a couple options.
Clean outside of tank scuff area and dry, 3M 4000, or even 5200 (the evil stuff) place a patch over the area.
If the discharge is not under fluid level:Relocate with an inspection plate and new through hole...
I could not find a regular poly tank to fit my application, so I made on from fiberglass and epoxy resin. 12 layers of glass, 3/8 to 1/2 thick. All access holes are in the top. SO far so good.