HELP torch coral suddenly closed

[Fishies2019]

Hello 15G tank all parameters in check ph 8.1 sal 1.026, 0.50 ppm ammonia and torch coral closed up and suddenly new algae in tank

 

[Zoaologist]

I'd get rid of that ammonia showing up in the tank.

 

[Florida Sunshine]

Ammonia sounds very likely to me as well.
Was this tank cycled? Did you also add fish?