Shift, you did a great job with the LEDs - the 2nd picture looks even too much light without the filter. It doesn't really matter if you get a HOB, except for the light. Too much light and you might have an algae problem, but if you keep the tank clean, you can always disable some LEDs to reduce the light some. But that's in the future. I'm having problems with algae and the 10w CFLs when I remove the screening under the lights.
I think you've probably got enough light with your current filter. I really wouldn't touch the plexiglas. The light is getting through now and it's a beautiful tank, rimless.
You're doing nice work, the plants look very good and growing. Did you test the ammonia yet? I rinse my arms and hands once before I go into the tank. Since you're working with test solutions it's not a bad idea. Eh, once I get going I don't bother with it - probably get rinsed off when I rinse out the test tube. Let me know about the ammonia level.