I found my biggest leopard skin upside down at the top corner of my tank this afternoon. Thinking he was unexpectedly dead I went to remove him, but he backed away and gingerly swam sideways and upside down around for a while trying to turn himself around but came to rest in some plants upside down?

Does someone know what is going on. I did a 30% water change yesterday and now notice that there is nitrate in the take so I have done another 30% water change.

I did introduce a school of cardinals (12) and 2 corydoras yesterday as well.

I have also read that this could be constipation or gas that the discus can pass and I read this can be treated with Epsom salts as it acts a a laxative, does this sound right? I am not sure.

Lost.