Are tiger barbs aggresive towards fantail guppies?

Hello. I have a ten gallon fish tank. The other day my five gallon fish tank cracked so I upgraded to a ten gallon tank. I moved all the gravel water and filter into the tank so that technically it wont have to be cycled again. I then put my fish (some kind of tetra the fantail guppy and another unknown fish) into the tank. These three fish got along great.I then went to the pet store and asked if tiger barbs were compatible with these fish, and the petstore told me yes. I brought two of them home but ever since then my guppy seems scared. could it be from the change in the environment or does it have to do with the tiger barbs?