I think my tank has cycled.

My ammonia level was .25 a couple days ago. This was the highest I saw, but I didn't test the water daily so I don't know if it got higher than that. Today the ammonia appears to be back around 0. Nitrites look to be between 0 and .25 and my nitrates have jumped up around 15-20.
I was thinking of doing a partial water change tonight and test again tomorrow.
I was also noticing a bunch of stuff floating around in the water and stuck to the glass. From reading it sounds like I may have some pods in there. The ones on the glass look like little creatures anyway.
Does it sound like my tank has cycled? It it safe to cautiously add another fish or two? Or should I wait it out a little longer. I was also looking at adding a couple more pieces of live rock in there. I have a few, but was going to try and get 1 or 2 nice sized pieces to add to the base. Should I add the rock and then see what the tank does before adding the fish?

 

hoping to get some local. Try to minimize die off, but I will still wait a week and see what the tank does.

 

tank has been up for 4 or 5 weeks. Substrate is mostly dry sand with ~5lbs live sand, Rock includes about 25lbs base rock and 6 or 7 lbs live rock from established tanks. Also added about 7 gallons of water and whatever else reefdumb sucked out from his tank for me. 2 or 3 weeks ago I added a couple damsels. 1 died after a few days and the other one seems to be doing really good. Then last weekend I added a dozen snails and a dozen blue leg hermit crabs and all those little guys appear to be doing well.