Most played cards in Merfolks:

1 Decks
Serendib Efreet
4 copies - 4 average
River Merfolk
4 copies - 4 average
Unsummon
4 copies - 4 average
Lord of Atlantis
4 copies - 4 average
Merfolk of the Pearl Trident
4 copies - 4 average
Counterspell
4 copies - 4 average
Mishra's Factory
4 copies - 4 average
Phantasmal Terrain
4 copies - 4 average
Blue Elemental Blast
3 copies - 3 average
Energy Flux
3 copies - 3 average
Psychic Purge
3 copies - 3 average
Power Sink
3 copies - 3 average
Psionic Blast
3 copies - 3 average
Boomerang
2 copies - 2 average
Control Magic
2 copies - 2 average
Amnesia
1 copies - 1 average
Braingeyser
1 copies - 1 average
Strip Mine
1 copies - 1 average
Mox Sapphire
1 copies - 1 average
Ancestral Recall
1 copies - 1 average