Yet Another Cycling Question

[jimmy40741]

I read something about someone on here going through a 'no cycle' cycle a few weeks ago, but I can't find the thread now. And I am wondering if that's what has happened to me. I set up a 125 about 3 weeks ago. I put in about a 2-3 inch sand bed and seeded it with about 30-40 pounds of live sand from my 75. I used about 30-40 pounds of live rock also from my 75 and another 50 pounds or so that I bought from someone else. I decided to try the raw shrimp method and have let 4 of them sit in my tank until they have completely rotted and disappeared, but I still can't get an ammonia reading. About a week ago while at home for lunch I got a slight ammonia reading (about a .25 or less) but I think it was a false reading because when I checked it again after work it was back down to 0. I hadn't been checking the nitrites or nitrates because I didn't figure there was any reason to since I hadn't even seen any ammonia yet. But I did check them this past weekend and my nitrites are at 0 and my nitrates are between a 10 and 20. So my question is, since I used so much from my other established tank (sand and rock) could the benificial bacteria already have colonized my tank to a level thats safe? In other words, could I have gone through a "no cycle" cycle?
Before anyone asks, I used all RO/DI water, Sal 1.025, temp 80.1F, PH ~8.2, Alk and Cal both in the good range, and the only thing in the tank is 3 blue legged hermits that hitchhiked in on the live rock.

 

[texasmetal]

Sounds like your tank could possibly be stable considering you did add so much already cycled rock. The sand should have caused some sort of spike if it came from your other already established tank though.
If you aren't getting ammonia readings or nitrite readings, and you have a tiny bit of nitrates, sounds like your tank's ready.
I would just add livestock REALLY SLOWLY though. Sometimes this kind of situation is like a time bomb. It could have a really hard cycle once you start adding stuff.

 

[jimmy40741]

Could you explain to me why the sand would cause a spike. I thought using sand from an established tank was just like adding live rock in that it also contains the benificial bacteria.
Also, I did another test this evening to see if there was any change from the last time I did a test this past weekend, and the ammonia and nitrites are still at 0, and the nitrates might be a little higher but they are still between a 10 and 20. The color just looks a little darker than last time but still not at the 20 mark.
There is a guy who is a member of the local reef club who is also a wholesaler and he made a post the other day that he wants to make a bulk purchase on livestock in a couple of weeks, so I've got at least another two weeks to make sure everything is stable before I'll be adding any livestock. I'm thinking that if I actually have cycled then in two weeks I should be good to go, but I just wanted a confirmation on it. Thanks for your help.

 

[texasmetal]

If you only read nitrates, then you have established the bacterias which convert the ammonia to nitrite, and nitrite to nitrate, so yeah, 2 more weeks and you should be ready to rock. Probably ready as is, after a water change.
The reason moving the sand could cause a spike is because an established living sandbed is going to harbor junk like detritus and once you disturb it you release all that stuff back into the water column. If it was a shallow sand bed it wouldn't be that big of a deal, deeper sandbeds being disturbed can reak chaos on a tank though.