Merfolk is also my favorite deck to run. I run a similar deck but I think you can still optimize this deck. Why not add 4x Glacial Fortress , remove the 4 card:Sea's Claim and switch them out for 4 Unsummon or Swords to Plowshares ? Seahunter is a nice addition too.
use some cards like, ponder, telling time, or sensei's divining top and for islandwalk sneak attack put some aquitect's will (enables islandwalk and card advantage) and or spreading seas
How about Mirrorweave ? Once you turn an opponent's land into an island, you can Mirrorweave your Lord of Atlantis . If you have 4 creatures, that'd be swinging for 24 dmg, not counting any of your opponent's creatures, as Mirrorweave would turn them to Lords too, further boosting your guys.
genuine139, do you realise that Tundra costs upwards of $300? Little bit expensive to be playing in a budget deck.