can lava rock be used in an aquarium to encourage it to turn to live rock? any suggestions of what to use? thanks.

Any rock can become live when beneficial bacteria are residing in it.

I love using lava rocks in my FW tanks, I never scrub them, and always incourage algea growth on them. There is also lava rock in the ocean (just look at Hawaii and Austailia), they have plenty of pores for organisms to start growing. So I would say its a good rock to make live rock, but I also believe that rchan is correct that any rock can become live rock (though Im not an expert in SW).

Lava rock is high in iron and other heavy materials which will leach into the water so be careful with rocks in an enclosed water system. In the oceans currents carry away and dilute the metals.

you can make your own. I will see if I can get the recipe if you are interest.
you cant use just any old rock because it will leach phosphates into the water column.

The ratio for DIY rock is 1 part portland cement, 4 parts crushed oyster shell.
make your mold of the shape you prefer add sand to the mold then the mix above allow to dry remove from mold and cure for 5 weeks a live seed rock or two will help seed the DIY rock and will become live and encrusted with purple coralline.
you can buy hypo allergic cement that contains much less lime to cut the curing time lime will cause high ph and is what you want to cure out of it.
imo this tank needs much more rock but you get the idea.

Very interesting.

Some people use macaroni in the mix to add pores and such. The problem with making your own that I've seen is it really has to soak a good while. 5 weeks might be on the quick side to leech out all the stuff you don't want in your tank. If you go the makin your own route you can find the crushed oyster shell at a feed store.

macaroni???? lol its Christmas not April fools

it's true! It rots during the curing process, so what you end up is porous.

here's an ehow article that lists elbow macaroni in the ingredients list...

http://www.ehow.com/how_5591489_make-artificial-living-coral-rocks.html