We have 5 serpae tetra in a 10 gallon tank. We've had them for about 5 months or so. We just returned from 8-9 days of vacation and it looks like one of them is going to die any second. It's laying down on the rocks at the bottom then will get startled and start swimming weakly before laying down again. I did a partial water change right before we left and just did another one when we returned. I used an automatic feeder that has a drum on it and rotates at certain times throughout the day. I also had the hood light on a timer so it would come on during the day and turn off at night. Any last ditch effort I could make to save it or should I just consider the sick one a loss and take him out of the tank? Thanks in advance...I'm a newbie so not sure how to handle this.