http://www.infish.com.pl/wydawnictwo/Archives/Fasc/work_pdf/Vol7Fasc2/Vol7Fasc2%20-%20w08.pdf
Here an article I found about some experiments done with catfish.
One of the things they mentioned is that the fish are less aggressive when in darkness.
I cant understand what 'Group D (25 szt.*dm-3)' means. The szt.?