I got a question why is that heater just dangle there is it being used? The filter wont kill them unless they are like tetras but even then my tetras don't get sucked to the filter. They probably died of poor water quality or as stated above dominant male. Also do you put on like spray deoderant or something like that? that could of got in the tank and poisoned them.
Just read your post so no on the spray.
Just read your post so no on the spray.
