hi guys.i have a question abt my betta. last time i used to take this as my hobby during primary school. then now after so many years i start to have them back.

my betta is ok at first. after few weeks his tail start to have small holes and became bigger and bigger untill now quite teruk already. i dont think is physical damage or something coz one my betta fell into basin coz i mishandle it while i change water.then his tail got few place koyak. but after less than a week recover ady.

so i would like to ask what actually happen to it's tail. and what should i do to help him recover? thanks