Got a couple done up for my tank and just like the idea from many years back when I first saw them in a LFS. Just like the idea of a plant floating in the middle of a tank.

 

 

 

are you using a bio ball for the float or foam?  What are you also using as a weight?

That one I got from Pisces Enterprises a company we deal with and it just uses a lead weight but in the days gone by it was manly java fern in a onion bag in the shape of a ball and weighed down in a similar way. 

Because the lead weight doesn't leech any nasty heavy metals into the tank

I made mine from bio balls and had them attached to other ornaments/driftwood to hold them down. They are currently free floating. Flame moss and peacock doers ally well on these. You just have to remember the lower half doesn't get as much light and won't grow as quick! They are awesome and the shrimp will graze on them all day!

I will probably replace the lead weight with something like a stainless steel nut or similar - I think a planted tank with the a few of the depth charges would look awesome a bit like a take from Avatar - well not quite but close anyway.

 

There are some guys in Turkey who have already created a "Pandora" tank & it looks spectacular!

That looks cool squiggs any idea how they got the rock to sit like that?

Couldnt you use styrofoam/polystyrene balls in the tank? Did a bit of a search and seems like it doesnt appear to leach

Looks like they have attached them to the back of the tank. I think newbreed is onto it with the bioball idea - you want something buoyant but not too buoyant where it is too hard to tie down.

Now i just need some bio balls and weight :P 

I think one I read said he used pumice stone. Would that float?