The one thing that I haven't seen answered here is the "why" part of waiting 4-6 months. Basically, as living things decay in your tank (algae, for example, but other bacteria as well) they produce ammonia. When ammonia levels in a new tank start to rise, a new bacteria colony is formed that eats the ammonia and produces nitrite. As the nitrite levels increase, a second colony of bacteria forms that "eats" the nitrite and converts the nitrite to nitrate. Nitrate is pretty much the end product of waste in your tank unless you use a nitrate reductor, which would further break down nitrate into nitrogen gas and oxygen gas. Otherwise, the recommended water changes will just as easily reduce nitrates in your tank.
The reason for waiting 4-6 months is that it takes approximately that much time for all of the appropriate bacteria colonies to form in significant amounts in your tank. Otherwise, the levels of ammonia or nitrite in your tank would spike, killing your fish in the process.
As you set up your tank, take weekly readings of ammonia, nitrite, and nitrate. You'll see each one spike in turn until the appropriate bacteria colony forms in large enough numbers to counteract it...it's really quite an amazing process and a heck of an education in chemistry if you can get the breakdown reactions and understand them.
And yes...Angels in general are very VERY picky about water conditions...definitely listen to your lfs and wait!!! Otherwise, you'll be wasting some hard-earned cash.
Good luck! Hope this helps.
-Dave Melczer
