Odd cycling characteristics

[Sinibotia]

Hi all,
A week ago I purchased a 10 gallon all in one that had just been set up as a display at the LFS. The tank was set up with about a pound of live rock from a mature tank and the rest dry rock, as well as live sand (come to think about it not sure the exact details on the sand). I've tried to cycle it fishlessly the same way I cycle pretty much all my tanks, with clear ammonia. However, when I add about 1-2ppm of ammonia, within 24 hours:
-Ammonia drops to 0
-Nitrite stays at 0.25-0.5
-Nitrate holds steady at around 10-20 ppm, although this may just be the nitrite showing up as a false positive.

It's almost as though the ammonia is being consumed by an outside process as there has been no spike in nitrite or accumulation of nitrates. However there is no macroalgae in the refugium nor significant algae growth in the display or otherwise, plus the lights have mostly been kept off. Filtration right now is just some carbon and a filter floss sock. Not really sure what's going on here. Any insight is helpful!

 

[blaxsun]

If you have some mature rock and live sand, you may have enough beneficial bacteria already (even with the lights off).

 

[Sinibotia]

If you have some mature rock and live sand, you may have enough beneficial bacteria already (even with the lights off).

question is, why would there still be 0.25 nitrite? even when I let it sit without adding additional ammonia that 0.25 is still there. I've checked the kit on tap water, a freshwater tank and new saltwater and it comes back 0 on those so it isn't the kit. plus wouldnt I expect nitrate accumulation?

 

[blaxsun]

question is, why would there still be 0.25 nitrate? even when I let it sit without adding additional ammonia that 0.25 is still there. I've checked the kit on tap water, a freshwater tank and new saltwater and it comes back 0 on those so it isn't the kit. plus wouldnt I expect nitrate accumulation?

You mean nitrite, yes? There's always going to be some nitrites present, as ammonia is converted to nitrite which is then converted to nitrate.

 

[Sinibotia]

You mean nitrite, yes? There's always going to be some nitrites present, as ammonia is converted to nitrite which is then converted to nitrate.

Yes I meant to say nitrites. So I should never expect 0 nitrite the way I see in my freshwater tanks? I didnt test it prettymuch ever in my previous reef and I know it's not toxic like it is in freshwater but I was still under the impression it would drop to 0 as the tank matured.

 

[blaxsun]

Yes I meant to say nitrites. So I should never expect 0 nitrite the way I see in my freshwater tanks? I didnt test it prettymuch ever in my previous reef and I know it's not toxic like it is in freshwater but I was still under the impression it would drop to 0 as the tank matured.

Correct. Unless you're seeing ridiculously high nitrite levels (which you're not), I wouldn't be concerned. There's a prevailing trend to actually not test for nitrites (not nitrates) going forward after a tank has cycled since the real parameters to be concerned with are ammonia, nitrates and phosphates (but less so for nitrates).

I run a lot of bio blocks/media (MarinePure, etc.) in my tank that convert any free ammonia or nitrites to nitrates, so I'm sure if I were to test I'd get a reading of near zero nitrites. You indicated you're running filter floss and carbon (I assume in a media caddy), so you can always add some small MarinePure hexagons in the bottom chamber to help with your bio filter.

 

[Sinibotia]

So then what's the deal with no nitrate accumulation? I'm getting 10-20ppm reading even after adding ammonia 4 or 5 times the past week, and it doesn't appear to have changed at all from this past weekend to today. Is it possible that there's already anaerobic bacteria processing nitrate too?