Right now my Cloyster knows Ice Beam, Spikes, Surf, and ummmm something else. But its ability is Shell armor, im pretty sure, And I just realized how GOOD Ice Shard is with Skill Link. Should I redo the cloyster but with Ice Shard and Skill Link?
Cloyster is not a bad pokemon, and has been used plenty of times in OU, it is a hard pokemon to use correctly though, and heavily relies on other tanks and special sponges i.e Swampert/ Blissey.
As for Ice Shard or Ice beam, it depends on your team. I personally like Ice Shard better for my spiking cloyster because I am not trying to deal massive amount of damage to my opponent through attacking. Besides, Cloyster is rather on the slow slide.