Planted Tank Guru
Join Date: Aug 2007
Location: Hendersonville, TN
The Petsmart "frill plant" is actually some species of Myriophyllum. I can't think of the exact species right now, buy you could probably google it if you really cared that much. I have some in my tanks too, and it looks totally different now than it did in the store. I have much shorter and fewer leaves, and the plant did undergo a partial melt to get that way. It really likes high light and CO2, but even then is a medium grower for me.
p.s. You can also check the tag at petsmart that gives the scientific nomenclature right under where it said "frill plant". That'll give you the definite answer.