Neverending Nitrites during Fishless Cycle

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Colt17

Aquarium Advice Apprentice
Joined
Jul 1, 2009
Messages
41
Location
Allen, TX
I am a pretty patient guy, but this one is testing me for sure. I have been fishless cycling for 7 weeks now. 29 gallon tank with HOB filter, sponge filter, air stone, pfs, one small live plant on driftwood (this was my seeding), fake plants and fake rock. I dosed ammonia (no surfactants this time) to 5 ppm and about 4 weeks later started to see a reduction in ammonia to about 3 ppm with no nitrites visible. A few days later nitrites finally showed up at .5 ppm and rose to 5 ppm within a few days. By week 5 ammonia was dropping to 0 within 8 hours after redosing to 2-3 ppm daily and the nitrites dropped to 1 ppm. By week 6, ammonia stayed the course and nitrites dropped to .5 ppm. Nitrates have been about 8 ppm since week 5. After week 7 I still have nitrites at .5 ppm and am scratching my head wondering if anything is amiss. I'm sure I just need to be patient for a little while longer and I'll get over the Nitrite hump, but just thought I would check this wealth of knowledge for any known problems or suggestions to help. By the way, my pH has always been 7.8, but around week 6 dropped to 6.8, not sure if that matters during cycling. Thanks in advance for any help or encouragement! Wife is pretty sure we will never have fish at this point (she is not quite as patient!)
 
Frustrating, isn't it? It's odd that you got stuck at 0.5ppm. I got stuck at 5ppm forever, but since yours started falling and never finished that's odd.

Keep dosing ammonia once daily.

What test kit are you using? Maybe you have a bum kit? Have an LFS check the level for you as a confirmation.

Put in a small pinch of regular flake food. Crunch it up as finely as possible and add it to the tank, sometimes the traces in there can be beneficial.
 
Thanks Neilan!
I am using the API Freshwater Master Kit. I'll bring a sample to the LFS and see what they read. I did the flake food as well and that's when my nitrites started to fall. Odd, the nitrite spike only lasted about 3 days and I would have thought the nitrates would be higher as well. Funny, I was craving to see purple in that test and now I can't wait to see blue again.
Thanks for the great feedback!
 
If you have nitrates, the nitrites should have came down. Are you sure the nitrite test had not gone wonky? Try testing a known pure water sample & see if you get zero on the test.
 
Good thought Jsoong. I tested the tap water and zero nitrites, tank water still at .5. I'll see what the lfs reads anyway. Other than just waiting, I figure a pwc couldn't hurt.
 
Well, I just checked my pH again and it is now at 6.0. I'm guessing this might be causing the nitrite issue. I'll go ahead and do a large pwc to bring the pH back up and see if that helps.
 
On Sunday night I did a 50% water change and it brought the pH back up to 7.8, nitrites still at .5 ppm. Monday night the pH was down to 7.4 and nitrites were at 2 ppm. Ammonia is still going down from 2-3 ppm to 0 within 12 hours and nitrates were about 10 ppm. Seems I am having another nitrite spike. I'm afraid I am having some water issues due to soft water and low KH. I will have to get a test kit for KH and GH as I have not tested that yet. I'll test KH to be sure, but I would think I am going to have to buffer the KH with a chemical or crushed coral (do crushed sea shells work?) Thoughts anyone?
 
See how low it is first. In general buffering isn't usually a good idea as it causes swings in your tank that can be detrimental. If it's really really low, maybe something would help, but let's see what you're dealing with first.

it's not uncommon for pH to swing wildly when ammonia and/or nitrItes are present.
 
The higher the Ph the higher the ammonia, which causes nitrates and nitrites to slow down. I am at a 7.4 Ph with an ammo level of .50 after a night long of WC's and testing and WC's and testing.

What is in your tank that is causing the Ph to drop nearly 2 points? that in itself will cause havoc on the biological enviornment within the tank itself.
 
WD, I guess it is the small piece of driftwood I have. It is only about 4" x 6" x 3".

I have tested the water hardness and believe that is the problem. Good news is Nitrites are now at 0!

Here are tonights results
Ammonia - 0
Nitrites - 0
Nitrates - 0 (Not sure why these went from 20 to 0)
PH - 7.2
GH - 214 ppm or 12
KH - 35 ppm or 2

I tested tap water and had the following results
GH - 161 ppm or 9
KH - 18 ppm or 1

I'm not sure exactly what this means other than I know the low KH does not provide much of a buffer and can lead to high pH swings. I do have about 2 lbs of crushed shells in the tank as well if that matters.

Can someone enlighten me on what this means and what precautions I need to be taking.

Thanks in advance for any help!
 
odd you get 0 nitrates. 7 weeks isnt uncommon some times it takes time for the nitrite eating bacteria to be in the numbers they need to use them all up.

when you test your water leave it out over night and check the ph also.
 
my ammonia was just at 8.0 yesterday at 3pm cdt. its at .50 now, tomorrow .25

I cannot control this tank with the sand bed as thick as it is, I am scooping it out tomorrow when I do the final WC for fish reintroduction.


what size tank was it again? I think driftwood is a natural buffer and will cause the Ph to drop slightly but 2.0 is alot of drop. How are your fish doing now?
 
I cannot control this tank with the sand bed as thick as it is, I am scooping it out tomorrow when I do the final WC for fish reintroduction.
how thick is it? having a deep substrate shouldnt effect much of anything.
 
In general buffering isn't usually a good idea as it causes swings in your tank that can be detrimental.

I must disagree with your there. Buffering is supposed to reduce pH swings. <This is assuming that you are actually changing the buffering capacity of the water, & not just dumping in a bunch of pH Up or Down ... THAT would cause pH swings, as those agents are not good buffers.>

Getting back to the OP's water results:

The low KH of 1 is prob why there is pH instability. When ammonia is converted to nitrates, acid is produced. If there is not enough buffering capacity, the pH will drop. This seems to be more a problem during fishless cycling, & may moderate with a real fish load. However, with unstable pH & low KH, increasing the buffering capacity is a good idea. <Crushed coral is the agent of choice, but you can also use crushed shells, limestones, or even baking soda.> Note that you should have a pretty good understanding of water chemistry before doctoring the water, and you would need to slowly acclimatize new fish to the doctored water. Also, large pwc's may be tricky, as you now need to match pH & KH in addition to temp.

Why the NO3 dropped from 20 to 0? What test kit are you using? With my Haugen kit, the presence of nitrites will mess with the nitrate test, giving a false positive. <Although only at levels of 1 or more>. Perhaps this is what is happening here?
 
WD, it is a 29 gallon tank and with my KH so low I think I will probably remove the driftwood. I have not added fish yet.

Question - If driftwood acts as a buffer to lower pH, would the crushed coral also act as a buffer to raise pH? Or would the crushed coral just raise the KH enabling the pH to remain constant?

I think not changing the water during my fishless cycle exhausted the KH and created the pH swing. Hopefully, with weekly 15% to 20% water changes the water will be more stable.

Jsoong, what level should I try to keep the KH at, I assume at least 4? It looks like the 2lbs of crushed shells is helping a little as tap water KH was 1 and tank water is 2. I am using API freshwater master kit, I will retest tonight and get a reading from LFS. The nitrate dropping does not make since, I do have one small anubias and a moss ball about 2" in diameter.

At least I know what is going on now with the water and what to monitor. About water changes, if I'm doing a 15% change, how close does the pH and KH have to be to the tank water parameters?

Thanks again everyone!
 
Well it looks like my tank is finally cycled! Water parameters are as follows:

Ammonia 0
Nitrite 0
Nitrate 10 (pretty sure I messed up the test yesterday)
PH 7.2
GH 12dh
KH 2dh

I am hesitant on trying to raise the KH at this point, so I will continue to monitor the ph this week. As long as it remains constant, I will do a pwc (15%) and add some fish!

Thanks again to everyone for the help!
 
Question - If driftwood acts as a buffer to lower pH, would the crushed coral also act as a buffer to raise pH? Or would the crushed coral just raise the KH enabling the pH to remain constant?.......

Drift wood don't really act as a buffer. Drift wood releases tannic (& other) acids & uses up the existing buffers to lower the pH. <OK, chemically speaking, the tannins are buffers, but there isn't enough to really buffer the water -ie hold the pH steady.>

What cc do is to drive the pH to its equilibrium. <Which is 7.8 or so in pure water .... values will be different with other buffer present.> Given enough cc & time, the pH will approach equilibrium & stay there, in spite of addition of acids or base (within reason).

Crushed shells should act the same as cc. 2lbs should be enough to drive the KH up quite a lot, so I would not be surprised if the pH starts to creep up.

As long as the pH stays constant, the KH at 2 is OK. 4 might give you a bit more room for errors, (eg injecting CO2) but the resting PH of 7.6 might not be what you want.

With cc or other additional buffers in your tank, you don't want to do a big pwc with undoctored water as that will drastically change the pH. Depending on how sensitive your fish is as to how big a swing you can subject it to. I know goldies & other hardy fish can take a 0.2 change. Typically, this is a 10% or so pwc. <The new water will gradually change to the tank's equilibrium pH as more CO3 dissolve into the water.> Personally, I err on the side of caution & do slow water fill. I use a small hose to fill my tank after a pwc, and I run it in slowly over 1/2 hr or so. So even with a relatively small pH difference of my change & tank water, I still give the fish a bit of time to adjust. For bigger pwc, people would recommend matching the change water's KH to the tank's using bicarbonate (baking soda). <Or you can have crushed shells soaking in barrels of water overnight.>
 
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