Confusion around nitrite

[Yannick]

A week or two ago, I introduced a few guppies in my tank and they almost all died within a week. Upon checking the water, it seemed like a nitrite issue. My other fish in the tank are all doing fine but they are bigger so the fish store told me, guppies are more sensitive because they are smaller...

Since then I'm doing almost daily checks and since I ran out of strips, I bought new ones, but from another brand. I'm now using JBL Pro Scan which is the same brand as the drop test I'm using.
The cool thing about this brand is that it uses an app to give you the values by taking a photo of the strip with a reference card.

The weird thing... My nitrite on that test comes back as 0.25 mg/l while the reference card on my drop test shows 0.025 so that's a factor of 10 smaller! Is that a misprint in the reference card of the drop test or am I missing something?

I use osmoses water and when I test that, I also have the same value, 0.25mg/l from the strip test and 0.025 from the drop test. The same for the tap water so I think I might have an issue with the tap water, correct?

When I measured the water before I did a water change, the value came back 0 on both strip and drop test so it looks like I'm adding nitrite by doing a water test!

 

[86 ssinit]

You’ve got nitrite in your tap water. Guppies are not what they use to be. So anything could have killed them. How did you acclimate? .25 isn’t bad. Your bb should eat that in a day but being it’s alway there it’s got to be your test strips. Try a liquid test kit.

 

[dMog]

Your problem is more from using reverse osmosis water,,,you can use RO water BUT you have to remineralize it for fish...Fish do thing called osmoregulation...short story on that is osmosis,,,if there is no minerals the fish cannot do this properly or even at all ...And despite the "other" fish being fine, not they are not. the effects just have not yet caught up with the symptoms you are not yet seeing in them. Eventually the same thing will happen to them...can you post and test your tap water general hardness and carbonate hardness...s well the current general hardness and carbonate hardness in your fish tank right now. I would suggest to use tap water in your next partial water change, just use a good dechlorinator...i suggest Prime as it binds ammonia and nitrite for up to 48 hours and is highly concentrated..only a few drops per gallon as opposed to teaspoons per gallon of other brands, that may not bind ammonia

 

[Yannick]

I do reminerize the water so that's not the issue. Both my GH and KH are normal.
I've been using reverse osmosis for a year now.

My confusion is also the difference between my strip test (0.25mg/l) vs the liquid test (0.025 mg/l). I know strip tests aren't as accurate but that's a factor of 10!

 

[ProudPapa]

Regardless of the accuracy the test methods, 0.25 ppm of nitrites didn't kill your guppies. Both from my personal experience and from many posts here I'm convinced that most commercially produced guppies spend their time in your tank swimming around looking for a place to lay down and die.

I suspect you were told at the store that the nitrites killed them to keep from giving you a refund.

 

[86 ssinit]

.25 or .025 are not bad readings. They may just be from adding the guppies. Or from the guppies being dead for a bit in the water. Thing is that should be gone in a day or 2 with a working cycle. Being it’s not and it seems everything you test if giving you those numbers. Somethings up with the kits. Try testing a bottle of water.