FMQ tension setting
 

When I took a FMQ class some time back, the instructor told us to loosen the top tension on the machine. When I do that, loops from the top thread show on the bottom, rather than the top and bobbin threads meeting in the middle of the quilt sandwich. So I've started actually *tightening* the top tension before quilting. Does anyone else do this?

I agree with Tartan. Most longarmers will do a test stitch-out on the side of the quilt to check tension for those *specific* fabrics & batting used in THAT quilt before making adjustments to their tension. The only reason I can think of to loosen your tension from the get-go is if you're using invisible thread.

My first thought was the type of thread the instructor was having the class use. Was it by any chance a metallic?
I know this sounds critical of your instructor, but I would urge you to check out some u-tube videos showing adjusting tension - both bobbin and top.

Your observation that loosening top tension affects how the bottom looks. Adjusting bobbin tension will affect the look of the top thread. Different combinations of fabrics and threads make it necessary to get comfortable with adjusting tension on the machine. It's a little confusing at first, but once you get the hang of it, you'll be pleased with the result.

I"ve never had to loosen or tighten tension for FMQ. But as has been said, all machines are different. If it works on your machine that's fine to do.

Every so often I have to tighten the bobbin tension to keep getting a good stitch.

I just got my Janome back from the shop and the tension was adjust to a different value that I have been using all along, that could have been a problem with the working of the machine. I wouldn't touch the tension until you try a scrap block and move it around a good deal. I know that is what I will be doing first with these new setting. I always work with where I am before moving things around. It seems like I never get back to where I started if I move things. Best of luck getting it straight.