A week ago I bought 4 tiger barbs n from the time I bought them they stay in 1 corner of my 120 gallon tank all day, its only when I put off all the lights at night that thay start swimming around the tank, I really dunno wats wrong ??? I have 4 kribensis, 2 bala sharks, 1 pangasius shark, 1 gourami, 1 pike-nosed gar, 2 swordtails, n inserted my betta yesterday. R tiger barbs nocturnal? Or are they being threatened in some way?