Spacer Beads

why are my Bala Silver sharks twitching?

I have had my juwel trigon 190 set up 4 a month, with around 10 small gupies in. Today i added 4 bala sharks, and they all seem to be twitching, is this normal? What should i do if this isn' t normal?
Also i tested the water and the nitrite is 0, thanks

Twitching? As they swim? This may be normal, the tend to swim kind of like a minnow, very jerky in their movements. I had to return one of mine (small) when I was setting up my semi aggressive tank as he swam too much like "prey" for my needle nose gar to leave him alone.
So every thing check out, water quality wise? And the temps good? They should be fine : )