These this plant look healthy to you?

 

looks healthy to me

 

Looks pretty good

 

Sure does. What's your concern?

 

well..everyday when I check the tank..there will be stem floating..

 

lol that's the problem with stem plants they don't tend to stay put the best. Most likely your fish were playing in the area and loosened it. Its common in planted aquariums. Just stick it back in as long as it was still green and healthy.

 

Or consider plant weights. They'll hold down a bunch of plants, like you have yours planted.

 

what is it?

 

I dunno the name of this plant but I think its rotala green?because I pick it up behind my backyard..