are these muscles?

[reneeanneb]

hello it's me again.after trying to figure out what made my nitrate go up i was reading other posts about things spitting out white stuff in the water and it got me curious.i have several of these things on my lr ,they open and close and occasionally spit out cloudy looking water.btw my nitrate dropped down to 40ppm when i checked this morning (it was 80ppm yesterday morning)

 

[Devilishturtles]

My best guess is some sort of bi-valve. Doesn't look like a muscle to me. They have more of a triangular appearance, and aren't so flush with the rock. That's my best guess. Hopefully someone else with stroll along soon who knows for sure.

I have quite a few in my tank. They are quite cool.