I recently used clear monofilament in my machine to quilt with. Now I can't get the tension right. The top of the fabric looks good but the bottom is tangled up looking. I've been trying to adjust the bobbin thread and then tried the top thread tension. Nothing is working.

Is the top thread making a thread mess under the fabric? That usually means the top tension is too loose or the thread is not seated in the tension disk.

Remove the top thread from the machine.
ALWAYS RAISE the presser foot and rethread from the beginning.
Set the top tension at the midpoint and test your machine. Then adjust the tension until the two threads meet in the middle of the fabric.

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Generally, it is better to use monofilament in the top, not in the bobbin. There is also a problem with tension so our instructor had us tape a paper clip vertically about midway between the spool pin and the first thread guide on the top of our machine, set the spool behind the machine in a small cup and ran the monofilament through the paper clip and threaded as normal.

TIP: A general rule of thumb is that if the stitch looks bad on the top it is the bottom tension.
If the stitch looks bad on the bottom it is the upper tension. The upper and lower threads play
tug of war with each other.
Tension
You need correct tension on the top and bottom threads, but you must also have correct tension on
the quilt held between the rails. You should have a small amount of "sag" in your fabric. This allows
enough movement of your quilt layers for the needle to penetrate and make good stitches.
Before you start making adjustments to your machine ask yourself, "What changed?" If your machine
was stitching great and all of a sudden it has loopies on the back or puckers, "What changed?" Did
you just change the bobbin? Did you just lift the take up rail? Did you lower the take up rail after
finishing your last quilt? Did you recently change the needle? Did you just roll the quilt?
If the take up rail with the quilted portion of your quilt is too high, it will result in poor stitch quality. You
need a finger tip space between the quilt and the machine bed. Higher will result in poor stitch
quality, too low and the quilt will create a drag on your machine's movement.
Look at your bobbin, a sloppy wound bobbin will not create a good stitch. Make sure that the threads
on the bobbin are snug and evenly wound. Check to see if there is a piece of lint in the bobbin case

I would suggest that you don't use this thread, it is too fine for the tension device on a domestic sewing machine, and they just don't like it. Too strong, too fine. Its best used in industrial blind hemming machines, if you look at RTW trouser hems you'll often see monofilament utilised here.

I'm having the same problem. Even when I sew. The tension just isn't right. I have two machines now and both have done the same thing.

This is a problem with thread tension. The needle thread is too tight and the bobbin thread is too loose. I don't have one of these machines, but there should be either screws or knobs to adjust. Look at your manual. Here's a page I found on bobbin tension.
https://www.manualslib.com/manual/1022927/Toyota-Quilt-50.html?page=50

Tension on 9 is very hig, should be about 5

If the thread is shredding and breaking, there is an incompatibility of your needle, thread, and fabric. Could be old, bargain bin, or poor quality thread--does the thread have little "hairs" of thread lint sticking out of it--that's probably not good quality. Look for fresh, good quality thread. Try a brand new needle--a sharp if you are sewing woven fabric. Make sure the thread is not too big for the needle eye. Sometimes, a top-stitch needle or embroidery needle will work well on FMQ. (A top-stitch needle has a longer scarf which helps protect the thread during the multiple times the needle penetrates the fabric before the thread forms a stitch. Shredding means the thread is getting worn out before it forms a stitch. A piece of thread penetrates the fabric 10-20 times before it forms a stitch.) Could also be a snag somewhere that is damaging the thread.

Sewing Needle Troubleshooting Guide

SCHMETZ Household Needle Chart

Most FMQ instructions say the upper and bobbin tension should be the same, however, I find my machine works a bit better when the bobbin thread is just a little tighter than the upper thread. Then the bobbin thread does not "pop" up on the top of my fabric quite as much. It's probably something you will just need to experiment with in getting used to your machine.

P.S.--when threading your machine, make sure the Presser Foot is ALWAYS RAISED so the top thread will seat properly in the tension disk. Failure to do this will cause thread barfs (usually referred to as thread nests or bird nests) under your fabric. Also, before beginning your FMQ, ALWAYS PULL the bobbin thread to the top of the fabric, then hold both thread tails gently in your left hand while you slowly take the first couple of stitches.

How and Why to Bring up the Bobbin Thread

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Mono thread can develop a memory and curl itself around things. I hate the stuff.

If the top stitch is loose, then you need to tighten the bobbin tension: if the bottom stitch is loose, tighten the top tension. Hope this helps. It could also be the size needle and thread you are using for a particular fabric. Different fabrics require different notions.