I have introduce a pair of Kribs to my community tank a few days ago. The female is doing great but the male just sort of sunk to the bottom of the tanks and didn't swim around. Within the first 24 hours my male krib died. I returned him back to pet store to be replaced. The new male is now behaving the same way. Not moving, unless is being chased by the female. His fins are not moving much, gills and mouth are moving rapidly. The female is still doing great, ph and NH levels are fine. I have now isolated the male in a breeding tank so he won't be harrassed. Don't look like he'll make it through the night. Any suggestions? It is bad fish from pet store? or something i'm missing. My first time with Kribs.