Originally Posted by
JohanNeeda
BTW it is a Tern.
The nuts definitely need to be tight. If the chain is too long, it can be shortened. A chain tensioner would be an unnecessary complication; these are usually used on bikes with internally-geared hubs whose frames have vertical rear drop-outs. Re-positioning the wheel doesn't affect chain tension much, if at all, with vertical drop-outs. Your Tern has horizontal drop-outs.
Steve