It is a tank glass not acrylic
well,
it is on both coconut and glass..
i also have just discovered one more thing..
when i use my hand to touch the wall of inner tank, its kind of touching a sand paper, it is pretty rough.. o_0
i will try to describe as clear as possible..
well, basically the whole glass is full of very very fine white dirt, just that some of them is a bigger spot as u can see in the picture..
however, the bigger spot can be easily remove by just touching it softly..
those very fine dirt is pretty difficult to be removed, i really have to use some force on my finger to clear it
it is not slimy, not sticky.. i think it is fuzzy.. i never touch something like
that before..