Nitrates disappeared?!

[Colton]

I have a 20 gallon long FOWLR tank, with one blue damsel, 2 pajama cardinals, a hawaiian feather duster, and two blue legged hermit crabs. There is about 18 lbs of live rock. Well, I tested my water earlier, and:
Ammonia: 0
Nitrite: 0
Nitrate: 0
I am using a API master saltwater test kit.
The trates are gone! They were at 40 a week ago. I've done nothing except for 25% p



wc's every week. Any clue? Here's the tank.

 

[woody390]

How longs tank been going?

 

[bonniewoodruff]

I had trouble with the api test for nitrate. I got a different brand because I kept showing them at 0. With the sailifert test they were over 100.

 

[Colton]

About 5 months. It's a fairly mature tank.

 

[baron1282]

I thought Nitrates at 0 was ok as long as Nitrites were at 0 too? According to my test my Nitrates are at 0 as well. I had let it cycled for 3 weeks got the BIG ammonia spike than got the Nitrite spike, than everything went to 0. Everything! I proceeded to put two Clown Fish in my tank, and I am adding a Six line tomorrow. I did a test tonight to make sure everything was good for the Wrasse.

Everything reads 0, but the PH which is at 8.2.

 

[Colton]

I know there's.nothing wrong with it, but just the fact that its at 0 is odd. I've always had at least 5 ppm of nitrates. I guess I'm doing something right