i recently purchased plants off the internet,it was a batch of 25 plants,when they arrived i went to put them in the tank and bury them into the gravel they keep popping out the gravel and floating to the top of the tank,when i read the leaflet that cme with my package of plantd it says these plants should be tied to little pieces of bogwwood b4 being placed into gravel.does anyone know anywhere that sells cheap small pieces of bogwood?