When you have put fish in your tank, it still help you to get daily chance by click the shell in your tank.
Above the tank , beside the aquarium inventory, there is a bottle. Click the bottle, you can ask a randome question there. after that, you need to refresh the tank. when you go to tank again, you can ask questions one by one. if your awnser is picked by anyone, you'll win 250 gold. if not, only keep awnsering the random quesions of your tank, you can get at least 3k gold.