No ammonia, HIGH nitrites and nitrates

[erythropoiesis]

The tank has been cycling for 6 weeks.

I dosed ammonia to 4ppm and after 2 weeks ammonia levels started dropping and there was about 0.50ppm of nitrite.

During the third and fourth week I dosed the ammonia to 2ppm and nitrite levels were 5.0ppm+ so I did a 40% water change every three days to bring nitrite levels down to around 1ppm.

Fifth weeks there was no ammonia, 5ppm+ of nitrite, and 80ppm of nitrate. I did a 90% water change. Nitrite levels came down to around 2ppm and nitrate levels around 20ppm. Then i dose ammonia to 1ppm ever 2 days.

Sixth week was similar as the fifth week. 1 large water change.

Three days later after that large water change the ammonia level is 0ppm, nitrite 5ppm+ and nitrate 100ppm+.

Temperature ranges from 77-82 F.
7.4pH.
Mosses, hairgrass, and bacopa. No Co2.

How do I go about finishing up this cycle?

 

[nirbhao]

It's finishing! There are two different types of nitrifying bacteria you need. You have established the nitrosomonas, the stuff that turns ammonia into nitrite. Now you're working on building up the nitrospira, the stuff that turns nitrite into nitrate.

 

[coralbandit]

Stop adding ammonia and changing water?
When the nitrites hit 0 then dose ammonia to 2 ppm and see how long for it to zero out , you want 24 hours or less.
IMO every time you change water you are removing bacteria that you need to grow more of?The bacteria for nitrite take longer to form for many then the bacteria to convert the ammonia.
Every time you add ammonia and don't expect to see it raise some level I wonder why you added it [or changed water ??]
When you have zero nitrite within 24 hours of dosing THEN you should do MASSIVE water change to remove nitrAtes to safe level [20 ppm or less]...
Ammonia at 2 ppm produces MUCH higher ppm of nitrite so stop messing with changes and adding and ride it out proper.
Cal has math on ammonia/nitrite conversion but I will guess that 2ppm ammonia is aprox 15ppm nitrite ,soooo...No more ammonia till final test...

 

[NickNaylor]

Sounds like you are in step 2 of your cycle. Patience, patience, patience my friend. I agree with stopping ammonia addition - or at least reducing its frequency. Your "cycle" is essentially "stalled" due to a lack of bacteria that convert nitrite to nitrate. They're there - since you're getting nitrates - just not to a sufficient degree to actually clear out all of the nitrite that is produced from ammonia. I would minimize your addition of ammonia until your nitrite is essentially to zero. Once you're at that point, dose with a somewhat precise amount of ammonia (maybe 2-4 ppm) and see how long it takes for both ammonia and nitrite to be zero again. Once your filter can turn 2-4 ppm to all nitrates in ~24 hours, your tank is good to go.

I also agree with minimizing water changes. No real benefit at this point other than possibly keeping nitrates at a reasonable level, which you can do pretty easily once your cycle is complete with a couple of very large water changes.