Acrylic Tanks

[Tigger]

Thank you everybody for all your info and experiences. How do you get the coraline algea off the side of the tank? I don't think a light rub will get it off, will it? What do you use to repair scratches? Can you only get out small scratches? I have a few scratches on my glass tank, and I know the algea seems to grow in there first. I have to use a scrub pad to get into the scratches. How would you remove algea from the spots that are scratched? How can I tell what grade acrylic the tank is made from? Sorry for all the questions. I am planning on buying a new tank, and I just want to make the best decision that I can. The tank will be 180 gallons.