High Nitrate out of tap?

[Richard203]

im trying out algae scrubber since I always have high nitrate

 

[squint]

Lol. Food tilapia can live in sewage. That is meaningless based on your info. Some tilapia are very sensitive to poor water quality including nitrates.
Side note, API nitrate tests are very inaccurate. I use strips for nitrate tests. My water tested 40 ppm out of the tap. In reality it is about 5. I confirmed this with water dept. The BMFIC confirmed this, he is an aquarium dude and very concerned with water quality.

The water treatment plant most likely uses NO3-N units so 5 ppm or mg/L = 22.1 ppm NO3-. Forty ppm isn't that far off from 22 ppm considering how hard it can be to read test strips or the API nitrate test.

While I do have an API test kit, I bought it to test against lab grade equipment. I use a Hach DR/900 and the chromotropic acid method to measure nitrate.

I consider this the minimum for reliable nitrate testing.

I also recently purchased a nitrate standard solution and will use it to check all my nitrate tests but API in particular.

Check out this thread for more discussion on nitrate toxicity.

Note that there are dozens of studies that find that adult fish (basically anything life stage other than eggs/fry) can tolerate thousands of ppm nitrate. Even coho salmon, who are among the most sensitive as eggs/fry have a 96-hr LC50 of 1,310 mg/L NO3-N or 5,800 mg/L NO3-. Tilapia are probably more tolerant than most fish but not 100 times more (justifying a 20 ppm limit).