false test readings?

Question
I have a 35 gallon Amazon tank that is pretty densely stocked but stable for over a year with no "mystery" fish loss. I was using quick dip test strips and my nitrites and ammonia readings were always Nil- my Nitrates were consistently on the upside tho. I read this was often because of sludge build-up in the gravel and filter ( I have a penguin 330 with 2 bio-wheels)so I cleaned out the intakes and rinsed out alot of the sludge and replaced the filter packs. At that time, I also added some Tetra Blackwater extract. I had used other Blackwater extracts before- some said on the bottle they can mess up certain Nitrate/nitrite tests- but this one failed to mention that. (Before I tested before adding them) I tested again after my "housecleaning" and the Nitrites were at 5 ppm and rising! I totally panicked! I added Amquel+, did a 20% water change, added stress-zyme bacteria, aquarium salt- anything I could think of...the next day they were at 10 ppm!!!!I thought in rinsing the filter sludge out with tap water I had destroyed the bio filter and that all my fish were dying. More water changes, added Prime this time and bought "Cycle" and a bunch of new plants hoping these things would help. Still 10 ppm! The strange thing was- my fish were not acting stressed (aside from the fact that I had stopped feeding them and they were doing the hungry eye thing to me).My Danios even started spawning! Then I read that the test strips measure nitrogen too...so I bought a single test liquid test- with a tube- that measures JUST nitrite...and got a zero ppm result. Tried the quick dips and again got 10ppm. I began to suspect a false reading from the test strips. Should I relax and feed my fish?? Should I get ANOTHER test kit? I really love my fish- I have a 9 inch Pleco I have had for 3&1/2 years- since he was a little baby and would hate to have anything happen to the critters.....

Answer
Hi,
This seems very odd. The liquid test kits are a lot more accurate than the strips, so I would use those to take the readings.
I would get rid of the strips, they obviously don't work, and just rely on the liquid tests.
Putting more plants in the tank lowers the nitrate quickly, so you could try that. It is safe at levels under 30ppm anyway.
Good luck,
Kathryn