Nitrate WC question

[BabyBoyGreene]

Trying to wrap my head around this. I changed 10 gallons in my BioCube 32 and Nitrates went from ~20 to ~5... I repeated the after test twice. Took the pic about an hour later. Any ideas how this could happen?

Thanks!

 

[rmurken]

Colorimetric tests that rely on you to compare colors to a card will tell you generally what your nitrates are, but not with any precision. Theoretically you’d have dropped NO3 by about a third, but you dropped it by 75%. Same order of magnitude. Good enough. I’d just pat yourself on the back for cutting the NO3 level so much and then enjoy the tank.

 

[Randy Holmes-Farley]

Trying to wrap my head around this. I changed 10 gallons in my BioCube 32 and Nitrates went from ~20 to ~5... I repeated the after test twice. Took the pic about an hour later. Any ideas how this could happen?

Thanks!

Sure. Either you did not change exactly the fraction if the real water volume as you thought, it more likely, the kit is not as accurate as you are expecting.

 

[Dkeller_nc]

I'm going to go with more of a change than you thought AND the kit is not as accurate as you might be expecting. Specifically, your tank's volume is listed as 32 gallons. It's not clear from CoralVue's website how much of that might be taken up with solid filtration components, but judging from your picture, about a third of the tank's volume is taken up by rock/sand. So depending on how accurate your estimate of the change volume is, you might've changed one half of the water volume, and possibly as much as 2/3rds.

 

[BabyBoyGreene]

Thanks for the replies!

I’m estimating (WAG) that I have about 5 gallons of solid Rock volume. So that leaves me w 27 gallons give or take a gallon for the specs... 10 gallon WC = ~37% plus or minus 5-10% still doesn’t get me close to 75%.

Having given it some thought and doing some searching, I believe it’s possible the test isn’t measuring all the nitrate, so if I reduced my nitrate by ~15ppm it was probably closer to 40 before and around 25 after... instead of 20 and 5.

 

[blasterman]

It's an API kit and its claiming accuracy from 0 to 160 ppm.

Sarcastic laugh. There's a joke about API making pregnancy test kits but I wont repeat it.

Clinical / professional test grade kits dont have a fraction that range because it's not possible. Basically only the high range is in the ballpark or low range. Both cant be right. More than likely it's the low range.