Instant cycle on new tank?

I don't think adding a little water would hurt but it won't eliminate your cycle. I would suggest adding some beneficial bacteria (I've used microbacter7 for other things) and love it. It may help speed the process along but not eliminate it. Congrats on your new tank!

 

It's been a little over a week and I'm pretty sure my tank has cycled. I had an ammonia spike and then tested again at the end of the week and now just have high nitrates (20ppm). Will this go down on its own or should I do a water change? I have tons of critters in there, at least 6 min-brittle starfish, blue & purple mushroom, green palys and some creepy bristle worms(1-2).

 

A little over a week is a quick cycle.
Be safe and keep a bottle of bio spira or Microbacter7 (or any instant tank cycle in a bottle) around.
It'll save your tank if you start getting an ammonia or nitrite spike.

I also concur with earlier advice about death and taxes.

 

I hear you. The guy ended up giving me three good sized pieces of live rock along with some of his sand and filled up my tank with his water change water. Would this speed the cycle up that much? All of the hitch hikers I mentioned above have been doing fine. I am also going through a diatom bloom. I tossed a couple snails and hermits in to clean up and they are also doing well.
Thanks again for all the good advice.