hi all i have a 27 gallon tank thats about 3 months old now i bought some plants when i first bought the tank but im not sure the names of them anywayz one of them for the last 2 weeks have realy grown super fast!! i have it in the fron right hand corner of the tank and its sprouted right up to the top off the water and along the top all the way to the other side and im not sure if this is good or bad? it looks realy good the fish seem to love swimming in and around it but at what point do i cut it back and is this a sign of a healthy tank?

probably a lowlight plant then, maybe an elodea?
http://www.exciton.cs.rice.edu/faculty/won...um/elodea_s.jpg

or hornwort?
http://www.geocities.com/elgecko1989/hornwort.jpg

or cabomba?
http://www.akvariumas.lt/augalai/cabombace...caroliniana.jpg

thanks guppy man i think its a elodea i tried to post an image but no luck

Does it have stems with white colored "buds" at the end of any of the stems?

It's probably elodea or hornwort, as one of the other posters suggested. Try to compare it to the photos, and note that elodea will look more stringy if you have ~1 Watt per gallon of lighting (which is likely). Even in my tank with low light and low fish stocking (low fertilizer), elodea grows around 1/2 to 1 inch a day.

Either can be cut back and the cuttings replanted with the "parent."

If your fish love it keep it the way it is, then just trim it back when it gets a bit out of control.

You should trim your plants every 2 weeks.

I have this stuff, my god it gets out of control quickly! I had to prune my back shortly after I bought it because it doubled in size after 2 weeks. It's a good looking plant though when you keep it short and bushy, in my opinion.