maybe you should revise your mana base to complement this perfect mana distribution, I understand that most early drop are green and you want to start with green but with this particular build especially if you want to end the game with
tempest caller and play 6 non merfolk blue spells a better spread of 12 green/10 blue source would be more adapted, btw I tried this mana base and got screwed often with blue sources for spells(since
unclaimed territory doesn't work) so I strongly reccommend it. Nice brewing to everyone, merfolk is pretty hard to polish imo.