Wow. First pic looked like Pebble Beach course but now I see what you mean by full algae scrubber.Here is a side view.
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I thought about that.Man, I really liked your idea. I wonder if you do a mix of both how it would work out. So if you had just like 1/4 of sand on top. In a glass bottom tank it just looks dumb because it gets moved around and you see the bottom of the tank but in your situation any open patches would look like more sand underneath. I’m curious if the small amount of sand moving around would decrease the amount of algae that can grow on it.
Your plan is to do this on the bottom glass.I thought about that.
The problem : You would get a small hole in the real sand, which would look OK for a while since fake sand would show.
But then algae would grow in that hole, which might look even worse.
An alternative thought - fake reef bottom.
Buy some solid base rock. Cut it into fairly thin pieces, and glue that to a substrate.
Rough it up so it looks like a realistic rock.
Maybe add some sand in the joints.
I have seen that done on back walls of tanks. See below.
So basically you have a live rock bottom, so it is real, not plastic-sand.
Although all the nooks and crannies will gather detritus, so it might be pretty bad.
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More of a thought.I used to want to do a rock wall on the back glass.
Your plan is to do this on the bottom glass.
Snails are doing poorly.How are the living things doing?
Also, I got a couple of new Monti's .... from you!How are the living things doing?
Not me. He was very reef safe.Very sad indeed. Was this the one who was nipping at certain corals, or do I have you mixed up with someone else?