No, I have never actually had a positive test for nitrates, but I'll also admit to not having tested for them since the algae growth started. I observed an ammonia spike, a nitrite spike, and the a sudden algae growth, which I assumed meant nitrates were present.

The two zebras are still alive today, still active, and still eating, nothing's changed. I just tested the water, and if I'm reading this correctly, ammonia is 0-0.25ppm, nitrite is 0, nitrates are slightly above zero. There is a tinge of orange that wasn't there the last time I tested for nitrates. I'll keep doing daily tests for the rest of this week.