Nice game, the tutorial is clear and the fish are very polite.
I earned the 5K but then the game would not count my decorations towards the next objective so I couldn't progress any further. Perhaps that was the end of the demo.
It would be nice if hovering over a resource in the upgrade tree highlighted what upgrades require it. Also, sapphires seem a lot more useful to begin with compared to emeralds.
I'm not sure what else to suggest at this stage, it probably needs more small goals along the way because 5K is a bit steep and a lot of upgrades seem useful, but only much later when your base income is larger so small percentage increases are worth the unlock cost.
Keep up the good work.