I received 5 Margarita snails on an order when I ordered Nassarius snails. Grr... 4 of them died within 3 months, and one lasted about 8 months. My tank get no higher than 80. This is too bad because Margaritas are the best algae eaters out there.
You will still have to get an algae scraper for the the glass. I prefer a scraper to a magnet as I have found magnets scratch the glass real bad - just one little fleck of coralline on the magnet, and bam you get scratches from it. After wrecking two tanks this way, no more magnet cleaners for me!!
I am also a big fan of small conches (fighting or orange lip are great) provided the tank is 40 gallons or more. If the tank is too small the small type of Nassarius do a great job. I prefer Brittle Stars to Serpents, as I have known Serpents to eat small gobies. Grrr!
I also despise hermits, they are evil murderous jerks. I would call them worse, but these are public forums.
For snails I really like Stomatellas (they breed in the tank too). Astreas are great, especially if you can find the ones with the pointy star shaped shells (A. caelata), they are awesomest. I find Cerith kinda useless, both the black and the white ones. Bumblebees are in the same category as the hermits, oh and Tonga Nassarius belong in that group too. As stated, keep away from Turbo snails...they get huge. Trochus are great snails, but also get quite large.
The only crabs allowed in my tank are Emeralds, I think they do a good job picking at the rocks.
I don't like shrimp. Peppermints will eat Stomatella snails, and the rest I find to be pretty useless, and a pain in the butt at feeding time, the thieves.