thanks for the warning, just a quick diy CIF the creme cleaner for bathrooms etc does the same as the bottle of the more corse acrylic preparer stuff you have.
if you use CIF and a finger tip to scrub the large scratches out and then for the smaller scratches use a cloth and a bit of water to break down the CIF particles and that will be the fine grade preparation, then wash off and buff with windscreen wash diluted and paper towel and thenm swill with water to remove chemicals! hope this helps the pleco did a grand job of algae removal by the way!!!