Cycling Question. Is this too good to be true??

[Scavenger]

Well 8 days ago I put water and a cocktail shrimp that had sat dry in bucket for 2 days into my 20 gallon nano. The ammonia peaked on day 3 and the nitrates appeared. Yesterday, I noticed the nitrates had fallen from the previous day which peaked around 0.8 mg/l, so I threw in the first live rock and 3 hermits. Today I just tested and the nitrates are almost non existant. I have had fast cycles before in FW tanks but only when seeding filter media. My question is: is this too good to true? Did I somehow screw up? I don't have a nitrate kit yet ( I wasn't expecting to need it so soon) I'm hesitant to start adding any fish or delicate livestock in case the test results don't reflect the truth.