The material is 316 Stainless Steel and I have never seen or heard of this happening before but if there is two instances I would like to gather some more information. Both of you can send us an email at
support@avastmarine.com and we will send out replacements free of charge in the meantime.
I can't imagine any media we use in reef tanks being able to have a reaction with this material to cause this so I imagine it has to be abrasive but GFo should be much softer than SS so I am at a loss. Once we gather a little more info I will be able to send some details to our mesh supplier to find out if they have any ideas at all.