Too early for Diatoms?


New member
I've been away from the hobby for awhile,so I'm wondering if someone can help. I set up my 29 gallon biocube that's been sitting awhile. Rock was removed a while back and soaked and then dried. All new sand bed. It's been 16 days since my cycle was started. I'm getting a diatom break out at the moment. Water test was on ammonia, nitrite, and nitrates were undetectable. My question is it too early for a diatom breakout... I don't believe this tank cycled in 2 weeks, or can you get a breakout before the cycle?