Nitrate magically disappeared?

[Krissy]

Ok, I'm confused. My tank was cycled well before I got my 9 discus. Since the arrival of the discus my nitrate reading has been a max of 5 ppm, ammonia and nitrite 0. I do the wc when the nitrate gets to 5 ppm. Yesterday the tank again read 5 ppm of nitrate. I was going to bring fwd a wc today however on testing today I've got zero nitrate. Tested it twice to be certain and tested my other tank which tested 5 ppm. Is it possible for nitrate to disappear like this? Only other difference is the driftwood are now releasing tannins into the tank? Haven't changed my feeding schedule at all (4 small meals per day)

[sayid]

What is the make of your test kit , is it API ?
sayid

[Krissy]

Yes Sayid, API. Is there issues with this test kit?

[sayid]

No there is not any thing wrong.i just wanted to point out that when measuring nitrate especially you have to adhere to exact direction of the test method, i.e shaking of bottle 1 foe 30 sec before application also shaking of the mixture for 60 sec and then wait for 5 min .
avoiding that will give you false very low figures .

[Krissy]

Yep, been following those instructions religiously but reckon I mustn't have shaken 2 long enough as this morning got a read of 5 ppm so false readings. Better check my other tank as if it read at 5 y/day then it's probably much higher than that.