Hello, my eldest daughter and Mrs D wanted some pet goldfish so we bought a tank, filter, pump, some bits to go in it and two goldfish a few weeks ago. All seemed well. This morning I noticed that the bigger of the two fish, Stavros, was bullying it's smaller counterpart, Broccoli Head, going after it's tail and chasing it off (not sure of gender so I'm being neutral with he/she). This was happening when Broccoli Head was foraging around the gravel for food. When I feed them in the morning they're both too busy to argue until the initial feast of floating food is over and it comes to foraging. I haven't noticed this before and Stavros was pooing at the time. Does that make fish grumpy? A friend had one goldfish kill another and I'm concerned for the wellbeing of Broccoli Head. Any ideas?