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Discussion Starter · #1 ·
After just over 2 weeks of cycling my new tank (with bio-media from established tank) my parameters were:
ammonia 0.08ppm
nitrite <0.01ppm
nitrate 2.9ppm

So ammonia and nitrite seen to be relatively low, but not quite zero. I guess my first question is, do ammonia and nitrite have to be 0 to be considered "fully cycled"? If not, what is the cut off (ppm)?

Also, for those of you with test kits, what increments are the readings in and what is the lowest value above 0? I used instruments that can read down to 0.01ppm, at which point it is considered non detectable, or zero. That's why I'm asking this second question - if an ammonia test kit reads down to 0.1 for example, then my ammonia reading can be considered zero (and fully cycled?).
 

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In my opinion (and I'm a bit old school) If you start a new tank with established bio media you must have something in there to feed that established bio media or it will simply die off. I start tanks with established media all the time, I'm constantly setting up and tearing down tanks. But when I do start those tanks with established media, fish go in them right away. That, in my opinion is why you're not getting a "zero" reading. Your bio media has died because nothing is feeding it.

As per your test kit question, I have no idea. I rarely test my water, and my kit is a $40 kit and I'll bet it doesn't have the increments yours do. Either way, they should all three read zero...
 

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I wouldn't consider anything but zero to be zero. If another test kit only reads ammonia to .1, then it may indeed read zero where you're at(although not likely). If it does, it's giving a *false* reading, since we know the reading is in-fact not zero, but .08.

When ammonia and nitrite are at zero, the cycle is "complete".
 

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Discussion Starter · #4 ·
TheFishGuy said:
In my opinion (and I'm a bit old school) If you start a new tank with established bio media you must have something in there to feed that established bio media or it will simply die off. I start tanks with established media all the time, I'm constantly setting up and tearing down tanks. But when I do start those tanks with established media, fish go in them right away. That, in my opinion is why you're not getting a "zero" reading. Your bio media has died because nothing is feeding it.
I did add 2 Yellow Labs with the bio-media - sorry if left that part out
 

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I would have thought readings of nitrite or ammonia in ppb for aquarium purposes would essentially mean zero. After all, I don't think they sell ANY test kits from an LFS that can read values that low (?).

Of course no such thing as zero exists if you have the right precise instruments to measure values that low, unless your water is distilled.
 

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Discussion Starter · #6 ·
bernie comeau said:
I would have thought readings of nitrite or ammonia in ppb for aquarium purposes would essentially mean zero. After all, I don't think they sell ANY test kits from an LFS that can read values that low (?).
It's actually ppm, not ppb.

bernie comeau said:
Of course no such thing as zero exists if you have the right precise instruments to measure values that low, unless your water is distilled.
Exactly - that's why I asked the first question (original post). Let me ask it another way: Let's just assume we can measure infinitely low levels of the said parameters (for example 0.000000000000000000000000001 ppm). What would be considered the cutoff ppm to be fully cycled?

Even with a fully cycled/established tank, a test kit reading of 0 may not actually be 0. The test kit (presumably) just can't read values that low

Thank you for your input bernie :thumb:
 

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meangene714 said:
It's actually ppm, not ppb.
Yes I realize you have written in ppm. But anything below 1 ppm, you could say it's in ppb.

You have: 80 ppb ammonia, less then 10 ppb nitrite, and 2900 ppb nitrate, to put things in perspective. By the way 2900 ppb for nitrate is a VERY low value; great if you can maintain your tank below 20,000 ppb for nitrate or less :lol:

To put things in perspective, my test kit starts at 1000 ppb for ammonia, which can indicate a value of 500 -1000 ppb. Hypothetically, anything below 500 ppb ammonia is a reading of zero on my test kit. You only have 80 ppb.

At what reading in ppb you would consider a tank to be fully cycled, I do not know. What I do know, is that your typical aquarium test kit doesn't measure that low.
 

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Discussion Starter · #8 ·
bernie comeau said:
meangene714 said:
It's actually ppm, not ppb.
Yes I realize you have written in ppm. But anything below 1 ppm, you could say it's in ppb.

You have: 80 ppb ammonia, less then 10 ppb nitrite, and 2900 ppb nitrate, to put things in perspective. By the way 2900 ppb for nitrate is a VERY low value; great if you can maintain your tank below 20,000 ppb for nitrate or less :lol:

To put things in perspective, my test kit starts at 1000 ppb for ammonia, which can indicate a value of 500 -1000 ppb. Hypothetically, anything below 500 ppb ammonia is a reading of zero on my test kit. You only have 80 ppb.

At what reading in ppb you would consider a tank to be fully cycled, I do not know. What I do know, is that your typical aquarium test kit doesn't measure that low.
Thanks again bernie, that's exactly what I needed to know
 

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meangene714 said:
After just over 2 weeks of cycling my new tank (with bio-media from established tank) my parameters were:
ammonia 0.08ppm
nitrite <0.01ppm
nitrate 2.9ppm
I would say that if you take another test in a week, and you see the ammonia and nitrite stable at those values, and the nitrate increase, say to 10ppm, then you say the tank is cycled.
I assume you have used HPLC for those measurements?

Burt :)
 

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Discussion Starter · #10 ·
Burtess said:
I would say that if you take another test in a week, and you see the ammonia and nitrite stable at those values, and the nitrate increase, say to 10ppm, then you say the tank is cycled.
I think you're right.

Burtess said:
I assume you have used HPLC for those measurements?

Burt :)
I'm not sure what instrument(s) was used, but definitely not HPLC - don't have access to that beauty. But the methods were EPA 300.0 and/or SM 4500.
 

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when i cycled my tank it was a new process so i cycled for two months but after 4 weeks i added a school of white cloads to keep the filter cyle for good bacteria after the second month the tank was totally cycled i was checking my tanks lvls every week just to gat the experience my freinds have with there tanks about spiking and i was amazed at the process i would get some fish that u do not care about like white cloads to finish off your cycle for the next 2-3 weeks dont know if this will help you but try it . :fish:
 

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bernie comeau said:
I would have thought readings of nitrite or ammonia in ppb for aquarium purposes would essentially mean zero. After all, I don't think they sell ANY test kits from an LFS that can read values that low (?).
Which is why I didn't bother referencing such an unlikely set of circumstances. Based on your bolded statement, I stand by my original post; Only a reading of zero should be considered zero.
 
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