I've got 7 neon tetras in a 60l tank and they've only been in 2 days, but today I noticed the bigger one chasing some of the other ones around and when I looked closley there were little things coming out of the smaller fish, but the other ones were eating them as the were sinking down to go on my plants, is this normal? my ammonia 0 nitrite 0 nitrate 0 ph7 and I turned my air pump off caue i thought that might be strssing them.