Who Gives A Fish Forums

They can be a bit unsightly but you'll mostly see them when you disturb the substrate. Good thing you're already doing 50% water changes, just keep up the frequent gravel cleans and feed less. If you notice any uneaten food after a few minutes, net it out, feed what they can eat straight away. My ...

I've seen them come out of the substrate a few times, and when they do, it's pretty likely they're the same thing - they're a bit clearer in person, pics don't do 'em justice.

I'm pretty sure those white wormlike things are planaria, they're usually caused by leftover food. They're harmless to your fish, but to get rid of them, just do regular gravel cleaning and cut back on feeding a bit.