I thought it was probably there.
Like I said, I know a fair amount about them. Have any of you ever raised triops? They are nearly identical to horseshoe crabs. And not only was I planning on upgrading, but I was planning to give him to the calgary zoo one day. Or, I was thinking of having a nice open tank with some squid, perhaps he could live there. I have seen horseshoe crabs on shows that were 2' or larger, and at my LFS it says that too. But liveaquaria.com reccomends them for 30 gallons or larger, in fact for an info sheet my LFS simply printed this page.
Horseshoe Crab
(Limulus polyphemus)
Quick Stats
Minimum Tank Size: 30 gallons
Care Level: Easy
Tank Conditions: 72-78°F; sg 1.023-1.025; pH 8.1-8.4; dKH 8-12
Max. Size In Aquarium: Up to 2'
Temperament: Peaceful
Reef Compatible: With Caution
Diet: Carnivore
Origin: Atlantic Ocean
Family: Limulidae
The Horseshoe Crab is greenish brown to light tan in color. The dorsal part of the body is rounded, and it has a long spike for a tail. The Horseshoe Crab is really not a crab, but more closely related to spiders and mites, belonging to a group of animals called chelicerates. Horseshoe Crabs can grow quite large. The female horseshoe crabs usually grow larger than the males, with thier body reaching a maximum size of 12 inches in diameter. When small, they are very efficient scavengers and are great for aerating and maintaining sand beds.
The Horseshoe Crabs dig through sand and gravel in search of worms and any organic debris. It will move the substrate around almost nonstop in its search for food. They are reef safe, but when they attain a large size, can be harmful to fish and invertebrates, especially worms and clams.
Although it may find some food scavenging, its diet should be supplemented with meaty items such as pieces of squid and shrimp.
That was copied and pasted from liveaquaria, and thats the majority of what I know about horseshoe crabs.