@Teelaish
I love your justifying attempt of Aqua, but honestly, I fear it's just bad writing. He could always tell her he doesn't want to offend Aishira because of her family and her business, but he does not do so. Granted, I think Tiara wouldn't believe him either way, but Aqua doesn't know the extent of her trust issues.
So essentially, either Aqua sucks as a romantic interest and needs to polish up, and at least try to communicate, same for Tiara, or this story needs to be better thought out. Either way, as a couple, I hope both of them will have some character growth...
Also, they are faeries. The energy needed for water to move deadly like a tsunami would be the same for growing terrible plant life, I'd assume. As for nutrients, who says the faeries can't fix that and magically supply that? They made a flower blue for her and created a portal after all, so who knows what their limits are concerning their element. And even if they had to face more backlash than their sea friends - who says they couldn't just substitute the harvest with poisonous plants?
Just saying, I wouldn't want to mess with either faeries...
But I really like your theory that forest faeries choose less human interaction due to the backlash they can receive from their ire. I just doubt the author thought it out that much.