I don't know this would work on acrylic, but I used window tinting on my corner overflows.....from a distance it looks like it is painted, but if you want to look at the plumbing you can get closer and see if there is anything going on in there. And it is removeable in the case I want to get rid of it later, as opposed to having to scrape paint off...

I painted my previous tank blue (avatar), and prefer black personally....

BUt your set up is looking very nice...great job.