Combination of nice weather, easment of restrictions and Tasmanian exhibit being open resulted in what exactly was feared - Prague reached its daily limit of visitors around 1pm and had to close for the rest of the day.
Prague's mayor already announced that they are negotiating with the secretary of health to lift the limit as soon as possible.
It looks like many people had the wrong idea (like me too) that our zoos have no daily limit anymore. Lot of angry people who wanted to visit with their families but came too late are sharing their experience on FB and other media. To keep the limit but allow normal sale of tickets at gate was not so bright idea.