Female Guppy harrassing another?

[lunasalix]

I recently got 2 female guppies from my local pet store. One died that night from a bacterial infection in its gills. The other is doing great, so I got her a friend today. However, since I added the new female, my tiny original female has been following her relentlessly. She hasn't fin nipped as far as I've seen, but the other guppy is desperately trying to get away from her and she won't leave her alone. Could this cause my new guppy to die of stress? What should I do?

[madagascariensis]

Are you very sure that the original fish is a female? If, hypothetically, the original one were a runty male, that would explain the small size and relentless following of the female( and being a runt would also explain the reduced finnage and color that would make it be mistaken for a female). If you are sure both are female, well, both female and male guppies will fight for hierarchy so the original one might be chasing the new one as a sign of dominance. In this case, it should cease within a few days. If your guppy hasn't been significantly stressed previously, it should be survivable.

[mizzoutank]

tank size?
water parameters? ammonia/nitrites/nitrates?
other fish in the tank?

stress comes from small tanks, new additions, other fish, poor water conditions and poor health.

so we need all that info to help "de-stress"your guppies.

[lunasalix]

tank size?
water parameters? ammonia/nitrites/nitrates?
other fish in the tank?

stress comes from small tanks, new additions, other fish, poor water conditions and poor health.

so we need all that info to help "de-stress"your guppies.

20g long, heavily planted with silk and live plants in gravel substrate.
The tank also houses 2 ghost shrimp and 2 African Dwarf Frogs in addition to the 2 female guppies.
Temp: 75 degrees
pH: 7.4
Ammonia: 0
Nitrites: 0
Nitrates: ~10

Also, they seem to have settled their differences at this point. It may have been what the first poster said about establishing dominance. I'll watch closely for the next few days to ensure that they don't begin fighting again.