1st Tank Advice

try to get something alive in there.

I would find a fellow reefer and see if you can get a little sand, algae, etc from them and drop in. Maybe get a peppermint shrimp and throw in there.

 

Was the live rock "live" when you got it or dry? Was the live sand from a fellow reefer or bagged live sand off the store shelf? Since you are already at 35 ppm NO3 that's a sign that you had ammonia at some point and it went through the nitrogen cycle already. If you started with live rock you likely already have a functioning bacteria colony. I'm with Craig, try to add some more life to the tank and slowly increase the bioload. Continue to watch your nutrient levels and do water changes as needed (at 35 ppm I'd probably do one).

 

I think you're probably good to go but you can do as Bud advises to be on the safe side if you'd like. Ammonia and nitrite should be zero.. NO3 can vary. In terms of how much water to change for nutrient control, it depends on your target... which depends on what you intend to keep. I am a sucker for SPS which demand a low nutrient environment (I never see NO3 above 0.2 ppm in my reef tanks). Mixed reefs with soft corals generally do better with some nutrients in the water (around 10-20 ppm is probably fine). I believe you may start incurring invert losses somewhere around 40 ppm. Fish only tanks are generally fine for most fish all the way up to 100 ppm.

So if you felt like you wanted to drop your NO3 down to 20 ppm from 35 you'd need to replace 43% of your system volume. I'd roughly guess you have about 10 gallons of actual tank water so a WC close to 4g should get you about there. I'm not necessarily suggesting you routinely perform this large of a WC (but with no inhabitants for now you're fine). I'd actually be more inclined to continue to monitor to see how things trend. If they continue to climb after you've added things to the tank then smaller more frequent water changes would be advised.

If you're anxious to get some things added I'd do a small WC and go with a peppermint shrimp, a few blue leg hermits and a few snails. For that small of a tank stick with smaller snails since a death could foul up the water very quickly. If you're really impatient you could probably get away with adding the clowns but you'll want to monitor things very closely (I'd hold off a little longer). You can control the nutrients with water changes but be careful with larger water changes since you'll cause your temp to bounce around.

 

Here's an ammonia calculator: Calculator