+2 How do you tell them apart?
I have these in my sump to replace bio balls for over 8 years already and they are still in great shape. I think the fake stuff is heavier compare with same size.
http://www.majestickoi.com/Momotaro-Bakki-House-Media/Momotaro-Bakki-House-Media-p-535.html
This is the only agent here in the U.S .