I have multiple test kits for testing my water. Two different bottles of Tetra strips and two test tube kits. The test tube kits both show that my water is pure nitrate with almost no water.

The strips both show a lower level, but do not always agree with each other. I have another brand of test strips which generally agrees with the Tetra strips. This past week I thought my nitrate spiked to a ridiculous level and did a roughly 75% change and the nitrate levels did not drop a bit.
I used to be able to keep on top of this, but now every test I do has sky high nitrates except for the 180 I got from Bob with the sump on it. That one only shows moderately high nitrates. Also, my planted tank shows sky high nitrates as well and all it has in it is a 4 inch pleco and guppies.