Hi all, thanks for the comments.
All the fish n things, do actually get on very well. I have mixed cichlids and oddballs ranging from the 22" fire eel, 11" tire track eel, and the frog. The frog is actually a fun one to have, when I go in the tank, he comes up and sits in the palm of your hand.
The air comes from an hi-blow65 air pump, which is pushing 4000ltrs/hour, I have seen shops using smaller ones than these! lol
I have many air curtains burried under the coral sand (80kgs of the stuff).
The rock is quite special in that it is hand painted to look like fuji rock, it is not just plastic, but made of a strange plaster type material. There is around £350 worth of the stuff in the tank...believe or not. I had to silcone all the rocks together, to make it look like that.