View Full Version : Is my tank close to finished cycling?

08-24-2008, 07:20 PM
Hello everyone,

I'm currently doing a fish cycle with a school of zebra danios in a newly aquired 20 gallon tank. (I now know that fishless would be the better way to go, but I found this forum after I started, and some of the books I read before setting up the tank strongly suggested using fish.) I'm using a Tetra 30 Whisper Filter w/ carbon if it makes any difference.

My reading recently have been 0 Ammonia, 1 Nitrite, 20 Nitrate. My pH is around 7.4 (darn basic tap water). My question is, am I close to finished cycling? If I am understanding things correctly, the lack of ammonia and the prescence of nitrates indicates that I'm on the second stage of cycling.

Also, are nitrites of 1 high enough to hurt my fish? I've been frequently doing 25% water changes but (strangley) it doesn't seem to be lowering the nitrites much. My fish seem fine, acting normally, no clamped fins, I even found fry swimming in the water when I vacuumed the gravel while changing the water yesterday!

Thanks in advance for your responses.

08-24-2008, 07:26 PM
When you consistently get 0 ammonia and 0 nitrites you are cycled. Strange that you don't see a reduction in nitrites after you do a w/c. What kind of test kit are you using?

08-24-2008, 07:29 PM
I'm using a liquid-based API master kit (not dipsticks). I think I'll try another 25% water change today or tomorrow, maybe the first one was just not enough to make a difference. I thought it was strange, though.

08-24-2008, 07:49 PM
I'd do the w/c today to be on the safe side, but that just me. Had a bit of a scare this morning, so I'm more cautious than normally :hmm3grin2orange:. There's the good chance that your nitrites are just borderline, but better to be safe than sorry, IMO.

08-30-2008, 11:25 PM
Thought I would pull up this thread I started about a week ago to ask this question:

For the past week my nitrites have been at 1, and my nitrates have been between 10 and 20. Ammonia is consistantly 0. Should my nitrites be falling by now or is it normal for them to be sticking around for a while before the tank finishes cycling? I've been doing 20-25% water changes every 2 days to protect my fish from the nitrites getting any higher and feeding sparingly. See my first post for other information about my cycling tank.


08-31-2008, 12:02 AM
You may not have enough bio filtration for the bateria to grow on. You may need to increase your bio load ability by adding a little sponge of filter floss to your filter. (I suggest the sponge) This should give the bacteria enough room to grow a slightly larger colony and finish the breakdown of the remaining nitrites.

08-31-2008, 02:44 PM
Thanks for the response!

For filtration I've been using a HOB Whisper filter and it does have a sponge that is supposed to hold the bacterial colonies in addition to the carbon filter. Is this sponge not enough? If not, would I put the extra sponge or filter floss in the bag with the carbon?


08-31-2008, 02:54 PM
If you can replace the carbon completely with another sponge or filter pad. Carbon's usually only needed to filter out something undesirable in your water column, like meds after treating ill fish.

08-31-2008, 03:33 PM
I would just use a second sponge I wouldn't worry about the filter bag...

09-02-2008, 03:16 PM
Thanks for all the feedback!

I thought I might continue using carbon filtration even though it might not be 100% necessary because the quality of the water in my apartment is questionable at best and I thought the carbon might be able to help the water quality a bit, and at the least not hurt at all. Also, I had already bought a big pack of the carbon inserts.

I might get another sponge or some filter floss and just add it to the bag with the carbon and each month replace the bag and the carbon, but return the medium to the new bag. Would this be OK?

09-17-2008, 11:52 AM
Well my tank's finally cycled! :19:

Three days now with no nitrites or ammonia reading. When the nitrites start dropping they go fast. Thanks to everyone who helped me with this. Now to get some more fish :c2:

09-17-2008, 07:31 PM
Congrats! Yeah nitrites goes so fast! My case is only 3 days. Incredibly way faster than me waiting for ammonia to go down.

I think some of the articles out there need to be corrected mentioning that the second beneficial bacteria takes longer than the first one.