I have had this kind of problems and as Ferox has said some fish get realy stressed in a bag and will try and hide in the corners - if so i just release them a little quicker?
Also i know with corys they can release something into the water from there gills causing them serious stress and even death, if this apears to be the case there should/could be a milky like appearence around the gill covers on the cory - if so remove from the bag A.S.A.P{without any water going with the fish} and good luck[
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<p>Hi thought about time i updated this no2! Tank no1 = 2 retic rays{both males},1 syd greshoffi{22 years old},1 syd unkown,1 stripped dora,1 pim,2 B/Ns,1 dat quad{alcatraz}. Tank no2 - 7 uariulus barbs,6 diamond sharks{new},3 scissortails,1 danio,3 geo jurapis,6 B/Ns,1 plec,1 RTBS,1 Candy loach,3 pims.</p>