Hmm... doesn't sound like cabomba to me. I just got 2 bunches, and they're growing like weeds. That's with a 55w on a 55 gallon tank! Your profile tanks are listed smaller, so yours should be doing very well? It does grow upwards towards light, and produces very very fine, white hair-like roots at points along the stems. Do you have a picture you can post? Sounds more likely that you got some hornwort? That also grows quickly though, but makes a HUGE mess in a tank. It doesn't root, just floats around.
I LOVE my cabomba. And it's grown about 1.5" in a week!