Tank not cycling

[Schnertzel]

I inherited a 75 gallon saltwater aquarium 3 weeks ago. I brought the live rock from its old location, but pitched the water and sand due to how poorly the tank had been upkept by its previous owner. I purchased 80lbs of live sand, and set the tank up at my place three weeks ago. The tank also houses its 4 previous inhabitants - 2 clowns, a scopas tang, and a watchman goby.

Since setting it up, I have:
- treated daily with Microbacter7 for two weeks
- three days ago treated with a bacterial mix from my local saltwater store
- added 10 additional pounds of their live rock
- performed 0 water changes
- fed the fish daily
- performed water tests at least every other day

Here is my problem: ammonia, nitrite, and nitrate have all read 0 every single time I test! I even had the store test to make sure my kit wasn't bad, and they also tested everything at 0. How do I get this tank to cycle?!?

I have a history of this problem, as a previous tank of mine apparently went over a year before it established its cycle, despite live rock and fishes. When it finally cycled the ammonia spiked so high that it wiped out the entire tank. I would NOT like to go through that again. Help, please?

 

[James404]

If the live rock was from an established tank, it's very possible it is already cycled. Add some fish food and test again in 24-48 hours, if you have no Ammonia or Nitrites, your tank is cycled.

 

[thegrun]

+1, not only i it likely, it is a sure thing the tank did not need to go through a cycle, the rock had enough live bacteria to handle all the fish waste. The proof is that there is no detectable ammonia or nitrite after three weeks of feeding your fish. Feel free to slowly add more fish, coral or invertebrates. I would limit the additions to one or two fish per week so the bacteria can catch up with the increased bio-load.

 

[Schnertzel]

If the tank has properly cycled, shouldn't I begin to have a nitrate level? I thought that was the last step of the process, and the indicator that a cycle was established?

 

[mcgyvr]

If the tank has properly cycled, shouldn't I begin to have a nitrate level? I thought that was the last step of the process, and the indicator that a cycle was established?

Only if the tank (bacteria) is not able to perform "complete" denitrification which involves nitrate being converted to nitrogen gas (N2) which would leave the tank on its own..

Welcome to an established system..

 

[bertoni]

I agree that a tank with live rock is unpredictable. I suspect that the system is fine, and nitrate might never show up in your system.

 

[offtropic]

Dose with ammonia to a specific level (use Dr. Tim's to 2ppm or whatever). Test tank 15 minutes later to confirm presence of ammonia. Test the next day...if it's gone and your nitrites are also at 0 then you are cycled.

 

[Lsufan]

Dose with ammonia to a specific level (use Dr. Tim's to 2ppm or whatever). Test tank 15 minutes later to confirm presence of ammonia. Test the next day...if it's gone and your nitrites are also at 0 then you are cycled.

I wouldn't go this route being u have livestock. If it wasn't cycled u would have ammonia being u have fish in the tank. So I agree with the others that u didn't have a cycle, or it was so small u didn't notice

 

[mcgyvr]

yeah welcome to last week .. tank is already cycled and stocked

 

[drysea]

The poorly maintained tank probably had an army of bacteria at every stage of the cycle although through to N2 gas. When you changed all the water and threw away the sand you probably but the bacteria in the very thoroughly cycled rock under some stress. I would be surprised if you got a cycle out of that rock with normal feeding. However now that you have established a new steady state for 3 weeks, now addition of livestock may produce a mini-cycle. Probably not enough to matter though unless you go nuts.