My puffer loves the rock, i wake up and when i roll over if he sees me move from inside his little hole he swims out to the glass its so cute.
Ill try and sneak into my room and watch him when he doesnt know im there. Because when he sees me he just goes to the glass and begs for food!
green!!!!!!! Funny cause when i took him out of a tank that had alot of plants... (fake plants ) he seemed to not mind. but when i put these little twigs in there he perked right up whent over to them and started exploring. the ottos are liking them too!
Also i cut a piece of plastic from a lid off an old tank to try and slow down evaporation.
I wouldn't say they don't like rocks or caves, they just like anything they can explore. If its a solid rock structure that's pretty boring but it looks like you can swim through the rocks in the tank which provides cover and amusement