Nitrate drop?

[Scoot]

I added a few pounds of cured LR on Saturday, to my 75g that's in its first cycle (in the nitrite spike right now).

I'm getting an expected ammonia bump from die-off (up from 0.0 to 0.25).

I top-off with about 5g of pre-prepared SW today from evaporation, about 2 hours ago. I used Tap Water Conditioner from Aquarium Pharmacuticals as directed (as I always have).

I just did a nitrite and nitrate check - nitrites are still high, around 10ppm, but nitrates, which have been between 10 and 20 for a few weeks, is at zero! I've rinsed the test tube several times, thoroughly, and retested 3 times now, and nitrate is still at zero.

I thought to eliminate nitrate it took a massive water change. Is it possible the tap water treatment did this? Or is there a chance the cured live rock is doing something with it?

[Brenden]

First thing that caught my eye was.

I top-off with about 5g of pre-prepared SW today from evaporation

Use only FW for top offs. Using SW will increase the salinity in your tank to a unsafe level.

Any chance the earlier NO3 test where done wrong? You are correct in that NO3 will not just disappear like that without a WC. I have seen weirder things happen though. I would guess it is probably a issue with the test. What kind of test is it?

[Scoot]

SG was okay before (and is okay now) - lots of spray and salt creep, I'm losing some salt from that. The top of the tank isn't clean enough for me to be comfortable to just push the salt back in.

I've pulled a little water out too, for acclimating my fish from this tank into the QT tank, and from vacuuming some debris.

So this wasn't just replacing evaporation (I shouldn't have said "topped off" I guess). More replacement I guess than anything.

I've tested Nitrates every other day for a month, they were all consistent until today, I'm pretty confident I've been doing it right (been testing inground pool water for a few years with the same methods). Before today they were creeping up into the orange-ish 20ppm range. Today, bright yellow, pretty clearly at zero (although its hard to tell between 0 and 5 on this chart).

The test kit is also Aquarium Pharmacuticals.


(Later update)

About a half hour after my last test, the colors on the test have crept up into the 10-20 range, but this usually happened in the first 5 minutes. Maybe my reagents are bad...

[tecwzrd]

Did you mix the #2 bottle for 30 seconds before adding? Could have missed a drop or lost count in adding drops. I’ve gotten 0-5 ppm readings from that test for the last 6 months. Confirmed it with a no3 Salifert test as well.

AP tests expire also (as do most tests) so if it’s old it could be less accurate. The readings usually do only take 5 minutes but will also gradually darken with time. You can also “cut” the reading by using half the water, adding the same amount of drops and dividing that reading if half although it’s slightly less accurate. I only do that when the color chart is hard to tell between two different readings.

[cmor1701d]

The test are meant to be read at a specific time after the reagent is added. This is usually 2-5 minutes. Any reading after a half hour should be discarded. I prefer the Salifert test kits due to the sharp color change for most of the tests. It makes it easy to get a precise reading.

Are you testing the salinity or SG of your tank? You don't usually lose enough salt to salt-creep to make a difference if you are doing PWCs. A good quality hydrometer or refractometer is essential in this hobby.

[jhoelter]

Originally Posted by cmor1701d

Are you testing the salinity or SG of your tank? You don't usually lose enough salt to salt-creep to make a difference if you are doing PWCs. A good quality hydrometer or refractometer is essential in this hobby.

Can you recommend one? I have an OLD Deep Six Hydrometer and I'm just not sure it's giving me accurate readings. Is this one or the Instant Ocean Hydrometer any good? Or do I really need a refractometer to get accurate readings?

Thanks,
Jeff

[Brenden]

I would get a refractometer. Even the "cheap" ones are good. Check liveaquaria, marinedepot, and fishsupply (.com) for sales. Then check ebay.

[Scoot]

Yeah, regular SG, pH, Ammonia, Nitrite, and Nitrate tests.

Like I said, I re-tested 2 more times, same result each time. Even tried a different test tube in case something was fouling the test.

Checking at exactly 5 minutes. The test I have definately darkens (and is now reading much much darker).

I think I'm going to pick up a new test kit for Nitrate at least and try again.

[cmor1701d]

I would get a refractometer. Even the "cheap" ones are good. Check liveaquaria, marinedepot, and fishsupply (.com) for sales. Then check ebay.

Same advice here. I like the Salifert tests although the NO3 test does not have the instant color change I love about most of the others they make. Still, I trust the reading I get from Salifert.

[Scoot]

Got a new test (same brand, AP), but I'm back to reading around 10ppm Nitrate. Ammonia still zero, Nitrits hovering around 10ppm, but declining a tiny bit.