Okay so for a while now I have been trying to figure out what is wrong with my goldfish Neo. He floats upside down but only at night I spoke to a girl who has th same problem as me and she took her fish to the vet and they didn't know what was wrong. So I experimented today with him. Here is how it went.
Woke up this morning to see a healthy happy swimming right side fish
2 hours went bye and I feed him Repashy soilent green/super green mixer only 2 small pieces.
Came back an hour or so later I caught him upside down on the bottom of the tank.
He has been off and on like this since I have feed him the gel food this morning around 9o'clock
I want to say it has something to do with the fish food?