Very interesting, so in your opinion does it look like something that could be DIY’d? If one were able to get ahold of some the framing.
I’m thinking the etching could possibly be achieved with a light touch with a dremmel bit
Yes, it would be a fairly easy DIY job if you can get the materials. That framing that I linked might not be quite the right size, you just need the internal gap to be around 1mm larger than the sum of the sheets you are inserting in it.
So for example, I think the Lightscreen one might be around 12mm inside, and that takes the 3mm solid white rear sheet, the 5mm clear/etched sheet, and a 3mm diffuser sheet.
You could certainly do it with a Dremmel if you wanted, but it would take a looooong time - at a rough guess there's a dot every 5mm, so on a 600mm x 400mm panel that like 9600 or so dots!! I'd probably be more inclined to order it from a CNC shop, or find somewhere that actually make these etched sheets for light boxes already.
All that said though, by the time you've bought the three types of perspex cut to size, had the CNC work done on the clear panel, bought the framing and fixings, sourced the gradient window film, bought the high output LED strips, cable, connectors and power supply, and had some clips made up to hang on the tank - you're probably not that far off the price of buying a Lightscreen off the shelf.