I picked up 2 jewels only a couple of days ago, and they're settling into their new 20g home, but feeding time has me confused. Are they bottom feeders by nature? Because when I open the lid and put the spectrum pellets in, they look at me like I just fell out of a well. It floats there and they ignore it, until it starts to sink and then they go into a feeding frenzy on the food. Is this normal?