I have a 400 gallon inch thick acrylic tank. 96''x30'' It's a show tank in a business, and was pretty scratched up when I bought it. As a result, I let employees write across the front of it for an event we held in October. We used dry erase markers which were also used on a light-up board. Most of the writing came right off leaving no damage behind... however, for some reason, one particular corner left tons of small scratches in the shape of the letters that were written. These scratches didn't show up right away. It took about a month before we noticed them. I have a friend who works at the local fish store who told me they were "microfractures" and that my tank was going to bust in the near future. He has been wrong in the past, and normally I would dismiss such a claim if it were not for the fact that these scratches appeared after the marker was removed. I can't afford a new tank, and I really do not want to have to sell all of my fish. I'm wondering if anyone has anything like this on their tanks, and if they know if these fractures/scratches will get worse over time from the pressure of the water. I will attach a picture of the damage once the store closes and I'm able to take some semi decent pictures. Thank you!