Nassarius snails can do the sand sifting and they eat uneaten food, not algae. i happen to like how they emerge from the sand the second food is put into the tank, it's impressive to see like 50 of them just rise up to eat. I don't think any CUC is really needed if proper tank maintenance is done, weekly water changers, not over stocking or over feeding....
You can blow off the crap on the rocks, try a turkey baster that will get the gunk into the water column and it can be filtered out. I have found hermits to not be as great as people say, I only have a handful here and there amongst all my tanks and they never seem to be doing much. Then again, I really don't have any algae in my tanks, my 20g had a massive amount but a lawnmower blenny and a turbo snail cleaned it up in a week. lol