is it better to stack the rock with lots of place between each piece or nice and tight? :redface:.

Not going so well? :D

I like the look of a loose stack plus it provides lots of hiding places and allows more flow through the rockwork. The downside is it takes more room per pound of LR so if you are relying on the rock in your display tank for filtration you may run out of space.

You will want to leave places for the fish to swim through, add some caves etc. Ensure it is secure and will not fall over.

Spaces are important, not only for the fish, but for the flow. the tighter your rockwork, the more dead spots you will have. I love the look of arches, pillars, etc. You can have fun with the design, but make sure it's very solid. You don't want a rock slide, so, use zip ties, putty/cement and drill where you can to use acrylic rods and you will be golden. Just for reference, here's my rock work before and after:

http://www.mattdean.com/build/tvnewrocks.jpg

http://www.mattdean.com/build/tv3.jpg

Have a look at this thread it will give you some ideas.

http://www.reefcentral.com/forums/sh....php?t=1524985

got mine fairly open. neat watching the fish cruising through it