How Do You Catch Aron In Pokemon Diamond And Pearl Ds?

Get to floarama town and go east on the little bridge. Use surf on the left side of the bridge. Surf westthen north then west when you can goto land up and down. Go up in the grass use your poké radar.  You got most change in wiggling grass with stripes above it. How harder grass wiggles how better the pokemon.

If you already know where to find one at iron island the best way to catch one with a quick ball or use false swipe on it with a really high level pokemon to get it down to 1 H.P. Status problem or not use an ultra ball for a 100% catch

You have to go to fuego ironworks and use your pokeradar.(have to get national dex first)

Only found in diamond and only found once you have completed both of pokedex [witch means you have to capture all 493 pokemon] you will have to use the poke radar at the fugo ironworkes.