Waterlogged Mangrove Roots Cause Flowing Water Sound Even When Flowing is Impossible

I made an aquarium below my floor by first digging one layer deep, then putting water all over the floor.  Then I dug down with Respiration to make a deep aquarium, then filled the top floor with Mangrove Roots so I can stand, but still see the aquarium below.

With the floor being big, suddenly I hear an insane amount of flowing water sound effects.  I don't think that's supposed to happen.