fasting

Hi everyone, new at this both fish and forums so please excuse me if I get it all wrong. Had a filter break down while at work. By the time I got home it had already been standing for a couple of hours. Could only get a new filter the following day. By this time the oxygen was a huge issue...

He is on day two of fasting now since I noticed he was bloated. He's been sitting in the bottom corner of the tank. I've checked on him to make sure he's still alive, he doesn't seem to have any problems swimming, it just seems like it's more comfortable for him to stay there as he swims back...

So I ususally fast my betta fish about 2 days out of the week, every week. I was wondering if fasting my other fish (koi,goldies,corys,platys, tiger barb) would be alright as well? I know that platies poop A LOT, however i noticed that one of my platies had a really thick poop (sorry if that is...