Won't swim?

[a.]

I've had an axolotl for around Three months, and around two months ago I moved it into a bigger tank. In the old tank it used to swim around all the time, but in the new tank it hasn't since I put it in there. The only reason I can think of is that the old tank didn't have a pump, and the new one does. Maybe its too powerful? I asked the guy were I brought it from and he said to lay it on the bottom of the tank shooting up, but that has'nt done anything.
I can provide pics if you want.

I also brought two more axolotls a week ago and they seem fine together, no eating of each other, yet...