I thought I would mention this as I often get asked this question. You may notice your Oscar twitching occasionally. Don't worry too much about it, Oscars seem to do it occasionally. Don't ask me why, I couldn't tell you. I would imagine it's something to do with their nervous system. Mine often do it when they are cleaning rocks and shovelling substrate. You may also notice their tails quivering. This is also nothing to be concerned about. My female Oscar does it when the male touches her. Again, there is probably some scientific reason why they do it and I'm sure that someone knows. As long as you know there is nothing wrong, that's all that matters