Three different test kits - three different answers - but wh

[spdntckt]

Thought I'd share an interesting experiment....Today I got a hold of three different Nitrate (NO3) test kits -> mostly because my kit was showing abnormally high nitrates in the system. I tested according to the mfg instructions with samples of aquarium h20 (80 deg) all within 10-15 minuites of each other. Here is what I found:

Salifert Test kit -> Reads between 10 and 25 I would interpolate the actual color I got to somewhere around 15-20ppm. 2nd test gave exact same result.

Hagen test kit -> reads between 20 and 50ppm - though i would interpolate this one closer to 50 than 20 (approx 40). The colors are too darn close on this test kit to really tell. 2nd test gave approx the same result - i would interpolate the result as much closer to the midpoint between 20 and 50 than the 1st test.

FasTest -> Reads between 10 and 20ppm, but looks closer to the 10 color than the 20 color. Actually, the color itself doesnt even match, but the intensity of the color that did show is what I am comparing here. 2nd test yielded approx the same result.. but again the color change is so slight it is really hard to tell.

I should note that all of the test kits are well before their expiration dates.

Here is my 1st question -> which one do you believe?

My 2nd question is: Why do i have such high nitrates at all (any way I look at it, i appear to have >10ppm).

Some data on my setup:
I only feed the tank 3x a week (combo of Formula 2 and live brine. both soaked in Selcon).

Ammonia - 0
Nitrite - 0
Calcium - 420
Alk - 10.9dkh
P04 - <.03
PH - 8.1
Temp - 80

90 Gallon system, approx 2" live sandbed (all live.. i did not start with a 'dead' sandbed and seed it with live), combination of a few different types of LR (fiji, tonga, i forgot the 3rd, but around 80lbs). Water changes are approx 20% every month. Top-Off water is RO/DI and tests for 0 nitrates.

Mix of LPS hard and soft corals (about a dozen), one clam, and only a few small fish (cinnamon clown, regal tang, blenney, orange spot goby, basslet)

All of the tank inhabitants appear to be very happy. All the corals open up super large (actually, you can see pics of the tank from the link below). The system has been running only a few months, since 7/01. Does the sytem need to 'mature' more before the nitrates will drop?


thanks!

[ September 09, 2001: Message edited by: spdntckt ]

 

[Toadally1]

Scott - I would say that your system has just come out of the cycle stage and that the bacteria colony just hasn't caught up with the end product. I would give it a few more weeks and test again. I don't think there's much to be concerned about.

 

[JennM]

I agree with Toadally, that your tank is still new, just two months and a few days...give it time to "grow up". For a newer tank you've got more bioload than I had in 6 months in my 55...

As for the accuracy of test kits, most will advise you that the Salifert test is the best of the 3 you mentioned. Hagen...thumbs down. As for the Fastest, someone in the aquarium pharmaceuticals biz told me that they are made by the same folks that make Salifert (but I haven't verified this myself, I don't have cause to doubt my source), but of course, the quality would be a bit different.

IMO all hobbyist grade test kits have a plus or minus factor, as you are seeing in your results. Unless you fork out big dough (I think I saw Lamotte master SW test kit for $289

) expect to get funky readings.

The bottom line is, you are watching your specimens and observing their behavior. IMO that is the most important thing to "test". YES have and use test kits, but it's easy to spot problems by knowing your livestock. Test kits usually prove or disprove theories about what might be wrong.

IMO you should change more water. 10 % per week or 20 % per month is what I recommend, and what I do.

HTH

Jenn

[ September 08, 2001: Message edited by: JennM ]

[ September 08, 2001: Message edited by: JennM ]

 

[mweber]

I was experiencing the same thing so I simply took a sample of my water to the same people who test my will water. What I found was that the salifert was the best but only when used in the low resolution mode. My no3 is running about 8-13 so in order to test it in low resolution mode, I mix two parts of my prepared nitrate free changeout water with 1 part tank water and divide the results by 3.

My local testing org only charges me $5.00 to test for nitrates only.

 

[spdntckt]

Thanks for the feedback guys! I think i'll wait it out a few more months and see what happens...

 

[Chucker]

One thing I didn't see is two tests of each kit against a blank of RO/DI water. Kind of hard to tell what the base color is w/o checking for it.....

 

[Anonymous]

I would guess that your actual level is around 20ppm. Not really toxic, but if you're adding corals, stick to the hardier ones. As your sandbed matures, the NO3 will come down--you'll start to see bubbles in the sandbed and some discoloration when that happens. My tank has been up and running since the new year and my nitrates started at around 20ppm. They just went to zero about 2-3 weeks ago.

From now one, I'd stick to one test kit. A ballpark figure is all you need-- +/- 5ppm isn't going to make a difference.

Ty

 

[spdntckt]

Ahh Chucker - You got me thinking

So I re-ran two of the tests on RO/DI water. (I had to give the Hagen kit back to the owner - so today I only have the FasTest and Salifert)

Here are the results:

RO/DI:
Salifert - Both tests came up perfectly clear - 0 nitrates

FasTest - Slight brown tint on first test. Not enough to actually compare to the color chip, but definitely not clear like the salifert test. 2nd test showed a perfectly clear result

Tap water (scary.. good thing i dont drink this stuff!)

Salifert - (only tested once) - registered right smack dab in the middle of 10 and 25ppm! (probably around 15-20).

FasTest - didnt use it - claims to be for marine use only.

[ September 09, 2001: Message edited by: spdntckt ]