I'd love a way to keep track of the fish I've found, so when I get to the end and find I've only got 440 instead of 441, I can easily find the one I need to breed.

The tanks to hold 25 fish instead of 21.

An "instant" birth potion where you can get all the fish you'd like in a tank pregnant, then add it and have babies.
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Sleep, who needs sleep, I have fish to raise.