No Nitrate?

I did a nitrate test today and found that the wasn't any. Which is rather strange because two weeks ago it was almost off the scale. I think that either enough algae grew and used up the nitrate, or the test kit all of the sudden went bad. Salinity is still low, pH and alkalinity is good. I set a trap off of the old Ponquogue bridge. I got a few things yesterday and hopefully I will get more later on.

I'm making plans for the summer. I need to put a net over the top of the tank to prevent fish from jumping out. I need to divide the tank so I can separate large fish from small fish. And I still have to block some of the sunlight and set up the nursery tank.