I'm not sure more levels would really alleviate the problem
With more levels built in, the actual effects of getting to he next level would be less, and I think that would frustrate more players than anything else
My vote for additional interest is to be able to decorate the tanks as we like, change the gravel color, etc.
Maybe instead of being forced to put the decor in the tank we could have a "treasure chest" where we store the decor we buy, until we want to use it. It would also be nice if we could buy more than one of the items, so we can use then in more than one tank. I would have loved to have several peices of coral to build a reef in one of my tanks.
There could be backgrounds to purchase, different colored gravel, new decorations (i want a mermaid!)
it would help with some of the boredom that can occur when you get stuck in a breeding rut
the decor could affect how healthy fish are, some fish doing better with specific backgrounds, etc
The main thing I want to see is additional tanks- my idea is thus- allow us to purchase additioanl "personal" tanks for an exorbiant price. Once a fish is in the personal tanks, it cannot be moved back to the breeding/sale tanks, nor can breeding occur in the "personal" tanks - it should however, be able to be moved between personal tanks
that would allow us to collect our favorite fish, without making actual gameplay any easier
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Why is it that if someone tells you that there are 1 billion stars in the universe you will believe them,
but if they tell you a wall has wet paint you will have to touch it to be sure?