Tension woes...again....

I'm trying to sew some denim pants right now using a new denim needle (size recommended by my machine manual) and blue denim thread.  I've threaded and rethreaded the bobbin and top thread, cleaned the bobbin case, cussed:P, and double checked my needle. I cannot get the tension right on zigzag stitches and it is driving me nuts!  I'm a newbie and tension is going to be the sewing death of me!  It looks to me like the top tension is too tight (almost a straight line instead of zigzag...can see bobbin threads coming through).  The threads on the underside look loose.  I've adjusted the top tension down and don't see any difference.  What am I missing?  Thanks!

Is your denim thread thicker than the usual threads you've been using? If it is, then you may have to adjust your bobbin tension. Your manual should have some instructions on how to go about it. Basically, it's a little screw that you must loosen to account for the thicker thread.
I've had to do this when I used some heavy nylon thread and it made all the difference. Just be sure to adjust it back when switching back to your regular thread.

Hadn't thought of that Irene.  I'll have to try that!  Thank you!

I figured out the problem!!!  I'm sure it is something most advanced sewers know, but I had no clue!  I was using denim thread in my bobbin.  As soon as I switched it to regular, things worked beautifully!  My little one finally has a cute pair of denim ruffle pants..woohoo!!!

Glad to hear it worked out.