Flush made on turn, how much to bet....

[Haplo]

The situation below may seem common place, but that's is really the reason why I am posting this. Situations like this can happen a lot, and I'd like to take maximize these situations.

My image at the table: tight overall (I'd been at the table for 20 hands or so).

UTG+1 seems loose---He had 72$
CO-139 hands, 33/9.3/1.4 Had 57$
I had 50$

Full Tilt Poker
No Limit Holdem Ring game
Blinds: $0.25/$0.50
9 players
Converter

Pre-flop: (9 players) Hero is BB with 4[img]/images/graemlins/heart.gif[/img] 5[img]/images/graemlins/heart.gif[/img]
UTG folds, UTG+1 calls, 3 folds, CO calls, 2 folds, 2 folds, Hero checks.

Flop: 6[img]/images/graemlins/heart.gif[/img] J[img]/images/graemlins/diamond.gif[/img] K[img]/images/graemlins/heart.gif[/img] ($1.75, 3 players)
<font color="#cc0000">Hero bets $1.2</font>, UTG+1 calls, <font color="#cc0000">CO raises to $5</font>, Hero calls, UTG+1 calls.

Turn: 2[img]/images/graemlins/heart.gif[/img] ($16.75, 3 players)
<font color="#cc0000">Hero ??????

I want to make money and I want to bet. The question is how much? Pot (or do I scare them away with that bet.) 2/3 pot? ...