I have a silver molly that is acting really weird. Note, I'm new at this; I've had first fish tank since June, and I've had the Molly since September. A few days ago the molly started swimming head down and with a bent body. Once in a while, it swims normally, but most of the time it is in this position. It appears weak as well. We think it looks like it's dying, but it's hanging in there. Sometimes it even seems to have a burst of energy for no apparent reason, and acts almost normal for a short time. What is wrong with it, and how can I help it? Thank you.