Hi, I recently moved 8 neon tetras, 3 albino corycats and 3 male guppies from a 70L tank into a 130L tank. The guppies were already acting strange and fatigued before the move, but I brushed it off and set up my new tank and transferred all the fish over (new tank contains previously cycled media). Currently, 2 of my guppies have died. They were slow moving and floating strangely. They didn't want to move at all and kept letting the current push them around the top of the tank. Eventually one died, and then another. I currently have one left that I've moved into a floating container which he is fine in and has correct orientation, but as soon as I put him back in the tank his body sort of rolls around/goes upside down/to this side/gets tumbled around by the filter. They all lost their desire for food. Is this swim a swim bladder problem that they've ALL managed to gain? And just now I've noticed one of my cories is not eating much. They all sometimes randomly swim up to the top of the tank really fast and then back down again - they've always done this. But I have one Cory that swims rapidly upwards fine, but when trying to go back down, he spirals uncontrollably until he hits the bottom where he just sits. He doesn't not eat. The other two seem just fine. My tank parameters before and after were pristine. I never overfed my guppies. It's possible the cories got overfed since they pick up all the remains, but the one that is appearing to be ill/disoriented at the moment is the smallest of the three. Since I only ever had three cories, the healthier two would always pair and occasionally the ill one would swim along with them, but not oftenly. I'm not sure what exactly has happened to my guppies and Cory, how it happened or how I can fix it. I've had the cories and guppies for three months or so now. Any suggestions as to what happened? I'm terrible with fish medicine and diseases, I usually rely on preventative methods.