Most played cards in Merfolks:

3 Decks
Lord of Atlantis
12 copies - 4 average
River Merfolk
12 copies - 4 average
Counterspell
12 copies - 4 average
Merfolk of the Pearl Trident
12 copies - 4 average
Mishra's Factory
11 copies - 3.67 average
Psychic Purge
11 copies - 3.67 average
Phantasmal Terrain
11 copies - 3.67 average
Blue Elemental Blast
10 copies - 3.33 average
Psionic Blast
9 copies - 3 average
Boomerang
8 copies - 2.67 average
Serendib Efreet
8 copies - 2.67 average
Unsummon
7 copies - 2.33 average
Energy Flux
6 copies - 2 average
Strip Mine
6 copies - 2 average
Control Magic
4 copies - 1.33 average
Power Sink
3 copies - 1 average
Chaos Orb
3 copies - 1 average
Ancestral Recall
3 copies - 1 average
Seasinger
3 copies - 1 average
Braingeyser
3 copies - 1 average