I open KQo UTG+1 to $25 over UTG fish's limp; TAG grinder on the aggro side who posted $5 behind the button (CO) 3-bets to $85. My read is that he sees this as good spot to defend his $5 in position. I've seen him 3-bet light in and out of position a number of times; it's something he does regularly. TAG grinder on the button very surprisingly flats, fish folds and it's on us.

Stacks: Me and CO $1500 each. Button $1000.

What should we do and why?