hi am a newbie, had fish for 3 mths now. i have a juwel 125. i had 4 dwarf gourami (2 male,2 female), 2 common plec and 12 cardinal tetras. everything has ben going fine, as i registered here and just read the forums for advice. but yesterday i lost 1 of the male gourami, was at bottom of tank for a day and seemed quiet, i thought might be gourami disease.I did a water change as nitrate was high as due for water change and thought dead fish may change the level. went to do a check this afternoon and both my plec had died, they were both fine (or appeared so) last night. the rest that are left seem ok at the moment so will do another change as yesterday i did 30%. do you think i should change a higher percentage of the water?