My bathtub burps when I flush the toilet and I think these tiny worm like bugs with antennas are coming out….I used a small amount of bleach for a couple of days but am worried about killing important balance in the septic….what should I do??

Actually when we talk about cleaning the drains, I can understand that cleaning a drain completely with a brush is not possible. So, you could also take the help of drain cleaning gel for this. Some people also use Caustic Drain cleaners, but you should avoid using such cleaners as they tend to damage the pipes.

My bathtub burps when I flush the toilet
This indicates a partial blockage. This can be addressed in one of two ways.
You can pull the toilet and snake the main drain or you can snake from the lavatory roof vent. Put out enough cable to reach the base and 15 for more. The bugs you see sound like Drain Fly larva. Do you see any black flies that you didn't have before? Let me know, Tom