aggression

 advice please! have a 3ft tank which has only platys and guppies in it, recently added 3 (2 standard, 1 dwarf) gourami as was told these would be good community fish, however the largest of the 3 became very aggressive attacking all the other fish (unfortunately killing 2 in one night) i have...

Hello. I've woken up today to find that some of my neons, particularly the dominant male, are acting rather aggressive. Many of them, including the dominant male have developed a black tinge to their fins. This happened around a month ago, then it went away. I've tried looking for the cause...