Cliff Notes: Testing 5ml of my tank water pegs the nitrite test at 5 ppm+, if I do a 50/50 with tap and tank water, I get a 0.25 ppm reading. I'm using the API master test kit. What is the true nitrite reading of my tank?

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I've attached my maintenance logs for my fish tank. Ignore the color coding, I have conditional formatting set up to color code the readings and organize them into a quick visual guide so the trends can be monitored in relation to the changes I make in the tank. My notes on the side are the notes I've been jotting down to chronicle occurrences and trends that can't be quantified in a spreadsheet like health trends, algae growth trends, and any chemicals added, so I can view the after effects of the chemical additions. It's my little way of tracking my behavior and how it affects the quality of life for the fish.

Because of the anti spamming policies, you'll have to remove the spaces from my link to see my maintenance log. There is a space in "http", "www", and the first sequence of numbers between "455" and "225".

ht tp://ww w.flickr.com/photos/455 22549@N03/6865992651/in/photostream/lightbox/

Enough rambling, moving on.

Tank:
- 29 gallon, ~ 30"x12"x18"
- Top Fin Power 30 filter
- Small rock for the filler (the little pieces they sell at PetSmart, about 0.25 to 0.5cm long)
- Few plastic plants, ceramic hut and palm tree decorations, NO live plants yet

It was ran for about a week and a half with no fish, added 3 Tiger Barbs about a week before I started keeping a log of events. I ran it with no water changes for the first week and a half, bought the API master test kit and started my log. I added the Pleco and Danios far before the tank was established, I wasn't thinking at all and just bought them on the spot. All fish have been purchased from PetSmart (healthiest place in town, no LFS). I'm currently preparing a piece of Mopani for the Pleco, I boiled it for a few hours and it has been soaking in a bucket for the last day. I hope to add it soon, I may just toss it in and let the tannins color the water and let the filtration take care of the color over time. That wouldn't be bad for the fish would it?

I've been doing the chemical changes and kept getting 5ppm+ for my nitrite test, but my fish appeared fine, and were thriving after being in the water for a week and a half.I've been doing daily 50% water changes with no change in the reading, the same purple I'd been getting all along. I decided to do a 50/50 test of tap water (0 ppm) and tank water, and got 0.25 ppm. So is my tank water at 0.50 ppm?

It doesn't make sense that my tank water would read 5 ppm+ but when mixed 50/50 with tap water, read 0.25 ppm.

Good news, tested levels today, nitrates at 5ppm, ammonia at 0.25ppm, nitrites at 0.25ppm. It appears that my tank has completed the nitrogen cycle. No dead or sick fish either.