I knew a lot of salt water folks were interested in and using these; hadn't gotten seen a lot of freshwater people talking - but don't frequent those forums.
I have been taking underwater photos to try and do something similar; hadn't figured out the chemistry with freshwater yet.
What paints are you using, cjohns?
Edited to add:
It looks amazing, by the way!
I was wondering about salt water as well,I can see some advantages and disadvantages...
I used the Sakrete too, as I went to Lowes also.
I only used a few thin coats. The initial coat was a little thicker, but the 'color coats' where thin. I watered those coats down a bit. I let the background cure for several days, I can't remember how many. Then I siliconed it to the aquarium and let that set a few days. I let it set with water in it for a week or two.
Looks awesome! Have you thought of the river manifold design? I just did it in my 75, and it's super easy. Just make sure you buy some PVC cutters. You can have it together in 30min or less.
Do you have a link to the manifold design?