Definitely not a spaghetti worm...
It appears to share a more characteristic look of a caterpillar, but it has some things that I can't find on any anatomy diagrams of them. Caterpillars tend to have 3 pairs of front legs and then a gap followed by a bunch of feet that have a very different look. The rear feet on caterpillars do have claws but a whole bunch if looked at up close, not the small clusters like this did. Also if they have antennae, it's usually on top of their heads.
This looks like something that has evolved to live inside of a cave or tube, it has one pair of front claws that are hooked backwards and the rest are facing forward, so it would be efficient in retreating backwards??
It was alive and wiggling around amongst the detritus on the bottom of the bucket. The odds of this coming from outside the tank is extremely slim. I rinse my buckets right before doing water changes because I inspect the detritus after every water change with a flash light. There's a "possibility" that it was inside the clear vinyl hose I use to syphon (it was sitting on the floor) but I've been switching to to a new salt over the last few days so this was the second water change of the day. And it's winter time, I don't know bugs, but I don't think that there's any caterpillars roaming around these parts these days, I've never even seen one in the house.
Hi John LoL
