@Sean J advice

What plant that will grow very tall and dominant I'd you would like to use a one plant centre scape for a tall cube tank ?

 

I meant IF I
Blerrie blackberry

 

There are a few options for this... You get the different Cryptocorynes. the C. balansae would be awesome as a center plant, but you may need about 4 or 5 of them to start with and let them fill out by themselves.

Then you could try to get an Aponogeton ulvacius plant as well. They are bulb plants, but they can grow some serious leafage! Would also be stunning. Actually, this would be my pick.

I would avoid Amazon Sword Plants. Some are nice, but the moment they hit the waters surface, they will take so much care and pain and torment to keep the leaves blooming below the surface.

 

What about a tiger lotus though it would probably fill the whole tank

 

size of the tank will help us pick a plant.

 

Thanks for all the advice the tank L600 D600 H 1000 all in mm cube of note
If the sale comes trough