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Hello Everyone:
Need advice on really long fishless cycle. The problem - lack of nitrates.

Have 20 gallon tank, started fishless cycle 7 weeks ago.I'm adding Ammonium Chloride as a NH3 source.
Nitrites started to appear at in a week after starting cycle but no  nitrates. I've increased temperature from 78 to 86 degrees 2 weeks ago. Today I did 5 gallon water change, I have few plants in the tank.
Conditions: Temp 86 degrees, GH 4 degrees, KH 2-3 degrees, Ph in range of 7-8 (both Ph and KH are monitored, alcaline buffer added if needed).  Have Fluval C3 Power Filter with water intake extended to the opposite corner of the tank, this ensures good water circulation. Withing the first week I was adding SeahChem Stability, also adding Stability once in one-two weeks.
Dynamics: Adding 25 drops of Ammonium Chloride every 12 hours, this amount target Ammonium concentrations around 2.5 ppm.
In 12 hours Ammonium is 0 ppm, NO2 is 0.25 ppm, NO3 is 0 ppm.

I guess everything is set up in good order. Please advise on completing the fishless cycling - converting NO2 to NO3

Hi delta678, welcome to the forum!  

First, congratulation for doing a fishless cycling.  You are on the right track to become a responsible fish keeper. 

Second, I have looked at your problem.
In order to find what's causing the issue, I need to ask a few questions.  

1.  Have you checked the ammonia concentration with the test kit to make sure it was 2.5ppm?
Adding ammonia by calculation is good, but we still need to test it afterward to make sure the concentration was up to our expectation.  

2.  What kind of water test kit are you using?
If all your ammonia has been turned to nitrite on repeat basis, while nitrite reading is not going up over the weeks, then it is very likely you indeed have nitrate but you are not getting an accurate reading for some reason.

If you are using API freshwater master kit, the nitrate test is a little tricky.   It has been a while since I used this water kit, so I do not remember exactly procedure.    If I remember correctly, you need to add two different types of chemical compound into the test tube.   The one thing I remember is, you have to shake the test liquid for up to a minute before and after the mixture.  Otherwise the nitrate reading you get would be 0ppm.   (additional information: Finally remembered it, you need to shake one of the test liquid for 30 seconds to a minute before you even open the bottle)

Some other water test kits might also have the same tricky procedure.   Make sure you follow the instruction exactly to get an accurate reading.  It is very important for fishless cycling to get all the readings correctly.   

Hello Thor,
Thank you very much for the quick response.

#1 After adding NH4Cl I measure NH3 concentration In 30-60 minutes, it's around 1-2 ppm
#2 I'm using API freshwater master kit for NH3, No2 and NO3 measurement. I'm aware that NO3 measurement is tricky - first need to add 10 drops of chemical #1, then shake _vigourously_ for at least 30 seconds, then add 10 drops of chemical #2, then shake _vigourously_ for at least 60 seconds, finally wait 5 minutes. With the same kit I was able to measure NO3 20-40 ppm some time ago, so I'm confident that step #2 is done the right way.

Let me comment on the NO3 20-40 ppm measurement. 4 weeks ago I measured NO3 20-40 ppm but at the same time I had really high NO2 - around 5-10 ppm.
Also my tank stuck at high NO2 (> 5 ppm NO2) for a week or two. In order to finish cycling I did the following #1 increased temp from 78 to 86 degrees, #2  did 50% water change #3 reduce NO2 concentration to 1-2 ppm

Hi,
I am a little confused now.

In your first post, you mentioned "lack of nitrate" and "0ppm NO3". So I thought you have never had any nitrate in 7 weeks of fishless cycling.

In your second post, you mentioned 4 weeks ago you have had nitrate concentration of 20~40ppm.

So, which one is it?

By the way, you do not need to do partial water change to lower nitrite to 1~2ppm. Maybe 10ppm is too high, but it should be no problem at even around 5~6ppm. Nitrate is also fine at 20~40ppm, unless you see a sudden large drop in PH.

Increase temperature to 86F is one of the methods to speed up the fishless cycling, but you also need to increase aeration to make sure the water has enough oxygen for the good bacteria. Warmer water can hold less air.

Thor:

>In your first post, you mentioned "lack of nitrate" and "0ppm NO3". So I thought you have never had any nitrate in 7 weeks of fishless cycling.
>In your second post, you mentioned 4 weeks ago you have had nitrate concentration of 20~40ppm. 
>So, which one is it? 

My fishless cycling is split in two parts - the first = high/stuck NO2 and the second one = no nitrates. 
During the first part I had NO3 reading of 20-40 ppm but at the same time NO2 stuck to more than 5 ppm. 
During the second part NO3 reading is 0. 
Hope this should clarify things

>2.  What kind of water test kit are you using?
>If all your ammonia has been turned to nitrite on repeat basis, while nitrite reading is not going up over the weeks, then it is very likely you indeed have nitrate but you are not getting an accurate reading for some reason. 

Thor:
You made my day!
It's a bit embarrassing but I did not perform NO3 test the right way - I did not shake the bottle with chemical #2 for 30 seconds. 
I repeated the test following the original procedure and now NO3 reading is 80 ppm! It's bright red!
Thank you very much for helping me correct my silly mistake

Gladly I was able to help.


Now you actually have 0ppm ammonia, very low concentration of nitrite, very high concentration of nitrate. It means your fishless cycling has entered the final phase. You are almost there! The nitrate might need to be lowered through partial water change. Then Keep adding ammonia every day. Soon you will no longer get nitrite at the end of every day.

Keep it up!

If you have any further question or have anything you'd like to discuss, feel free to use this forum.

BTW after doing 80% water change the NO3 concentration is still around 10-20 ppm, this means original NO3 was around 50-100 ppm.
So I've been poisoning my tank for few weeks, this did some damage to the plants. Hope that the plants will recover.

Actually nitrate is harmless. Unlike nitrite and ammonia.

Even at high concentration, it will not directly harm the fish. Only in the long run, super high nitrite (something like 100~150ppm or even higher) will lower the immune system of the fish. Generally, we keep it at 40ppm or lower. 20ppm or lower for more fragile fish. Of course, the lower the better, but there is no immediate danger with nitrate.

Your plants see nitrate as food. If they are not doing well, it can be other reasons. Such as they are not getting adequate lighting, or not enough other nutrients. What kind of lights and plant substrate are you using?

I'm using Finnex Planted Plus 24 hours, substrate is small gravel (regular, from PetSmart)

I guess the lights are fine if you give your plants minimal 8 hours of "day light" every day.  No more than 12 hours in total light if you do not want an algae boom.  

For the substrate, plants are better off with plant substrate instead of regular gravel.  My favorite substrate for a planted aquarium is Eco-complete.

This is my aquarium, no fish yet

After 80% water change I did 25% change and then 25% change next day again (I was still keep adding NH4Cl targeting 2-3 NH3 ppm). Nitrate reading was still around 20-40 ppm. Finally I did 70% water change, Nitrate dropped to 5 ppm.
But now with cleaner tank I have less bacteria so the 12-hours ammonia level (measuring ammonia in 12 hours after adding NH4Cl) raised from 0 to 0.5 ppm. 12-hours NO2 is 0 ppm and NO3 is 10 ppm.

Now I'm getting ready for the fish again - dropped temperature to 78-80 degrees, dropped water pH to 7.00-7.10 while keeping KH around 2-3, keep adding small amount of NH4Cl (targeting NH3 1.0-1.5 ppm) and waiting till 12-hours both NH3 and NO2 level drop to 0 ppm.

BTW dropping water pH to even 7.1 AND KH = 2 degrees was the hardest one - my tap water is 9.4 (as I've already mentioned)

Actually today 12-hours levels of both NH3 and NO2 dropped to 0. NO3 level is 20-40 ppm I guess I'm going in circles.
So tomorrow I'll add some fish - 6 corys and 5 Cardinal Teteras. Wish me luck

Looking good so far.

Yes, it is normal for nitrate concentration to go up really quick near the end of the fishless cycling. The good bacteria in your filter is so sufficient at converting ammonia and nitrite. It is a good thing. Once you have added fish, their bioload will not be as high as the amount of pure ammonia you have been adding to your fish tank, unless you severally overstock your aquarium with too many fish. So the nitrate will never go up that quickly once you have added the fish. Once a week partial water change will be enough to keep the nitrate low.

Your fishless cycling is over as long as you no longer get a reading of ammonia nor nitrite 24 hours after you have added up to 5~6ppm (2~3ppm is totally fine too) of ammonia. You only need a few days to confirm it is really over. Then you are ready to get your first batch of fish.

A few suggestions. It might be a good idea to add a background to your aquarium. Something green or black. It is entirely up to you.

For the number of cardinals, you can get more of them without a problem. They are not messy fish, and they will do better in larger number.

I look forward to see your fully stocked aquarium.

Good luck!