Greetings! Okay a couple weeks ago I started this new 20 gallon tank. Yes, the set up was done knowledgeably...and I put 3 little (like an inch or so each) African cichlids in of them this Acei.

And everything has been fine. All fish have been active, eating and happy.

....until today. Didnt see the Acei earlier. Eventually found him hiding in dark corner by a rock....hyperventilating.

At first he would hide for a while and then stir about. Now he's trying to stay hidden and also...listing to the side some...and hyperventilating like crazy. Meaning he's getting

I mean...he was fine yesterday...and I know its not the PH. So then...what. I'm thinking if I don't do something fast...he's not going to make it to morning. Any ideas on causes and cures?