Cycling question - unexpectedly quick nitrite/nitrate readings

[Agent Kooper]

I've set up a 12-gallon nano tank. I put in about 15 pounds of live sand (purchased in a bag from Petsmart), 15 pounds of base rock (CaribSea fossilized/petrified reef rock) and the water two weeks ago.

About a week in, I poured in a bottle of Bio Spira, just for the hell of it, and because I didn't really know what I was doing. I've been measuring the water, also just for the hell of it, getting 0 ammonia/nitrite/nitrate -- exactly what I expected because I don't have an ammonia source yet.

I decided to put in one raw shrimp to start the cycle. I did this 24 hours ago. I just measured the water and got a reading that surprised me: no ammonia (that's not the surprise, because I know I was impatient on the test), but 3 ppm nitrite and 40 ppm nitrate.

I don't know how I'm possibly getting nitrite and nitrate readings at this point -- I was just looking for the first signs of ammonia. Is it possible my live sand and the Bio Spira already started cycling my tank before I added the shrimp?

This is my first marine tank, but I've been educating myself and these results surprise me given what I've read.

 

[IslandHopper]

Yes... the live sand (and rock?) likely already had some bacteria in it... but you got no nitrite readings till you had an ammonia source for them to feed from and produce the nitrites (and subsequent nitrAtes.)
24 hours is plenty of time for a chunk of dead flesh to start decaying and producing ammonia... that time frame and reading sound perfectly reasonable to me if the lave sand/rock was already seeded with bacteria.

(all based on my experience with freshwater... my salt tank is still in the planning stage ... building of THAT should start in two weeks.)

 

[Agent Kooper]

The rock was dry dead reef rock, so I don't think that would have contributed much to my readings. The impression I've gotten from this board and others is that the live sand doesn't contribute as much as good live rock. The biggest question to me is why I wouldn't have ever seen a single ammonia reading above zero prior to seeing the spike in nitrites. The only thing that makes sense to me is that the Bio Spira I added is messing with my readings.

We'll see. Good luck with your marine set up. I've had a few successful freshwater tanks and am stoked about the marine creatures I'm planning to get.

 

[Schism]

The rock was dry dead reef rock, so I don't think that would have contributed much to my readings. The impression I've gotten from this board and others is that the live sand doesn't contribute as much as good live rock. The biggest question to me is why I wouldn't have ever seen a single ammonia reading above zero prior to seeing the spike in nitrites. The only thing that makes sense to me is that the Bio Spira I added is messing with my readings.

We'll see. Good luck with your marine set up. I've had a few successful freshwater tanks and am stoked about the marine creatures I'm planning to get.

Bio spira is bottled bacteria, combined with live sand it is note than enough to produce nitrates right away and both are ammonia sources as both biospira and live sand will contain dead bacteria as well.

Your in good shape, just wait till nitrite is gone and you will be good to go after removing the nitrates through water changes.