Fishless cycle - nitrites high and nitrates climbing - Aquarium Advice

MarkC · 09-22-2003, 05:51 AM

I have a brand new 180l (50US gallon) unplanted tank which is on day 21 of a fishless cycle, which I have diligently followed to the (phase 2 modified) instructions.

I have an Eheim external thermo filter with new filter media and used no other bacterial source apart from sera nitrivec (which I know is rubbished cause how can there be bacteria in it....)

The ammonia stayed at 5ppm until the nitrite spiked at 5ppm on day 10, then kept adding half of the original ammount of ammonia and the ammonia tests have been zero ever since.

The nitrite has been 5ppm (the max on my test kit) since, which I know is not a problem for a fishless cycle.

BUT the breakdown of nitriIte to nitrAte is definitely going ahead as the nitrates climbed to 400ppm by day 16 (followed by water change) and then again to 400 by day 20 - another water change.

What I don't understand is that if SO MUCH nitrAte is being produced, and all of my ammonia doses (enough to raise the tank concentration to 3ppm) disappears straight away.... why do the nitrites not go down to zero?

I must have plenty of both groups of bacteria?!
I am guessing patience will pay dividends!
Do I simply allow the nitrAtes to climb above 400ppm (top of my test kit) seeing as I have no fish to be bothered or will this inhibit the cycle.

Allivymar · 09-22-2003, 09:27 AM

There simply may not be enough of the nitrite eating bacteria to handle the load yet. You obviously have some, else you wouldn't have nitrates. You may actually want to do a partial water change (maybe 20%) to remove some of the nitrites; high nitrite levels can stall a cycle.

tkos · 09-22-2003, 02:54 PM

If you want to see exactly what your nitrite levels are then I suggest you take a regular sample then cut it in half with whatever water you use to change the tank water with (ie tap water). Then take the result from the test kit and multiply by 2. This is a pretty accurate method and will show you exactly how high those levels are.

Congrats on taking the fishless route.

jsoong · 09-22-2003, 10:41 PM

My test kit - Haugen wet - states that there will be a false positive nitrate reading if the nitrite is high.

I tried it while cycling, and basically if there is any nitrite ove 1 or so, the nitrate will read sky high, but there really isn't any nitrate in the tank!

I wonder if your test kit has the same limitation as mine.

MarkC · 09-23-2003, 04:15 AM

Good point, but I don't think this is happening since my nitrite was >5 at day 10 and nitrates didn't climb until a few days later.

I have the sera test kit, which incidentally requires serial dilutions of aquarium water to determine high nitrate levels and I had applied this method already as described by tkos (thanks) a couple of weeks ago and found that the nitrite was around 8ppm.

Either way, I am persisting and I was just glad to get such a quick breakdown of my ammonia despite not having a proper bacterial source. It is still only 21 days after all, and hopefully not long before I can fully stock the tank!

09-22-2003, 05:51 AM	#1
MarkC Aquarium Advice Newbie Join Date: Sep 2003 Location: London Posts: 6	Fishless cycle - nitrites high and nitrates climbing I have a brand new 180l (50US gallon) unplanted tank which is on day 21 of a fishless cycle, which I have diligently followed to the (phase 2 modified) instructions. I have an Eheim external thermo filter with new filter media and used no other bacterial source apart from sera nitrivec (which I know is rubbished cause how can there be bacteria in it....) The ammonia stayed at 5ppm until the nitrite spiked at 5ppm on day 10, then kept adding half of the original ammount of ammonia and the ammonia tests have been zero ever since. The nitrite has been 5ppm (the max on my test kit) since, which I know is not a problem for a fishless cycle. BUT the breakdown of nitriIte to nitrAte is definitely going ahead as the nitrates climbed to 400ppm by day 16 (followed by water change) and then again to 400 by day 20 - another water change. What I don't understand is that if SO MUCH nitrAte is being produced, and all of my ammonia doses (enough to raise the tank concentration to 3ppm) disappears straight away.... why do the nitrites not go down to zero? I must have plenty of both groups of bacteria?! I am guessing patience will pay dividends! Do I simply allow the nitrAtes to climb above 400ppm (top of my test kit) seeing as I have no fish to be bothered or will this inhibit the cycle.

09-22-2003, 09:27 AM	#2
Allivymar Aquarium Advice Addict Moderator Emeritus Join Date: May 2003 Location: NY Posts: 4,355 Images: 15	There simply may not be enough of the nitrite eating bacteria to handle the load yet. You obviously have some, else you wouldn't have nitrates. You may actually want to do a partial water change (maybe 20%) to remove some of the nitrites; high nitrite levels can stall a cycle. __________________ aka Cycling Guru and the Ich Slayer glares at Terry and QTOFFER Card carrying member of FTAS & GCAS.

09-22-2003, 10:41 PM	#4
jsoong Aquarium Advice Addict Community Mentor Join Date: Aug 2003 Location: Edmonton, Canada Posts: 1,890	My test kit - Haugen wet - states that there will be a false positive nitrate reading if the nitrite is high. I tried it while cycling, and basically if there is any nitrite ove 1 or so, the nitrate will read sky high, but there really isn't any nitrate in the tank! I wonder if your test kit has the same limitation as mine. __________________ 75 gal FW with 30 gal DIY wet/dry/sump. 9 fancy golds, 1 hillstream loaches, 1 rubber-lip pleco (C. thomasi), 3 SAEs, planted.

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09-22-2003, 02:54 PM	#3
tkos Aquarium Advice Addict Join Date: Jul 2003 Location: Canada Posts: 1,423	If you want to see exactly what your nitrite levels are then I suggest you take a regular sample then cut it in half with whatever water you use to change the tank water with (ie tap water). Then take the result from the test kit and multiply by 2. This is a pretty accurate method and will show you exactly how high those levels are. Congrats on taking the fishless route.

09-23-2003, 04:15 AM	#5
MarkC Aquarium Advice Newbie Join Date: Sep 2003 Location: London Posts: 6	Good point, but I don't think this is happening since my nitrite was >5 at day 10 and nitrates didn't climb until a few days later. I have the sera test kit, which incidentally requires serial dilutions of aquarium water to determine high nitrate levels and I had applied this method already as described by tkos (thanks) a couple of weeks ago and found that the nitrite was around 8ppm. Either way, I am persisting and I was just glad to get such a quick breakdown of my ammonia despite not having a proper bacterial source. It is still only 21 days after all, and hopefully not long before I can fully stock the tank!