The Scarlet Hermit Crabs (Paguristes cadenati), is an attractive red colored reef safe hermit crabs that does well in tanks bigger than 15 gallons. Somewhat larger than blue legs, they are rumored to get along better with other shelled inverts, although personally I think all hermits they carry similar risks. They consumer hair algae and detritus, are hardy and have a decent lisfespan. We have them for a short time for $1, with a maximum purchase of 10 per shipment.
You can find them here, at ReefCleaners.org:
Scarlet Hermit Crab