I finished all available games and aquariums at the beginning of January.
Since then, I've been playing the treasure chests.
I recognise many of the games, and don't mind them being recycled. It can be fun to have another go at them.
But I do mind the paltry rewards for playing them.

When I was in the higher levels of the game, I'd receive about 2,000 coins per level won, plus occasional diamonds.
Now, I have to win 15 games to receive in total about 2,400 coins, a couple of boosters and ten diamonds.
The harder ones are taking me ages now, because I'm reluctant to spend 9 diamonds to continue a game, when I'll only receive that back after fifteen games. It doesn't make sense to spend more to win less.
I realise you want to slow us down, but it's getting pretty boring losing the same game over and over, so I'm playing less and less.

Also, I play on a Mac and haven't had the last couple of events to vary things - no Christmas for me, nor Valentine's.
So I'm looking at the same old tanks with the same old decorations; no 'special' fish or anything interesting.
I've heard on this forum about the new bomb, and bubbles floating across with things in them and all sorts of things, but they don't appear for me.

AND the aquasplash doesn't work for these treasure chests. So all in all, the rewards and incentives for playing them really aren't there.