Hi! I became a tropical fish lover shorty after Christmas. Have had a 55 gallon cycled tank with good parameters since. Have one rainbow shark, 8 neon tetras, five glow fish, three mollys, and a yellow mystery snail. Yesterday my pregnant molly started shaking off and on and today is spending time on bottom. Had water tested and all is well. No other fish showing symptoms. Did 20% water change Saturday. Could it be cuz she's pregnant? Wish there was a fish vet! She's my first fish. Thanks for any thoughts. I'm still learning.