High Nitrites Fishless Cycle

[daffers1986]

Hi all,

Currently on a fishless tank cycle. Bacteria is now present, has been for a week or so that breaks down ammonia, working with 3ppm, dose during the day and all is gone by next day.

BUT, I don’t have any nitrite breaking bacteria so I can’t keep the nitrite levels down. It quickly shoots up to over 10ppm. Tank 350litres so water changes are a real pain that often but I’m aware that high levels will stall my cycle. Any advice?

Edit*

A bit more info, and after doing a diluted nitrite test.

Nitrite was off the chart so yesterday did pretty much a 100% water change. Nitrite was then at 0.5. Dosed the tank with ammonia to 2ppm. Test again today, all ammo is gone (as expected), nitrates at 2 on the 1 part tank and 4 part tap test. So nitrite is back to 10ppm again. Is that even possible? And do I need to reduce this or can I leave it? Keep in mind I’m going to have to dose ammonia every day.

Any thoughts welcome. Cheers!

[Megalodon]

Two ppm ammonia becomes 5.4 ppm nitrite. You can dose less ammonia daily. I would watch pH and make sure it doesn't get too low. Other than that, just wait.

[daffers1986]

Thanks Megalodon.

At what concentration of Nitrite should I start to worry and look to reduce?

[DJW]

I have cycled tanks with as much as 40 ppm nitrite, so the cycle can still finish, but it will take longer, for two reasons. High levels of nitrite (>10ppm) have been shown to inhibit the growth of nitrifying bacteria. Also, if the nitrite is really high you won't be able to see when the nitrite-oxidizing bacteria have reached the strength needed to handle your 2ppm per day input of ammonia. Instead you will be waiting another several days or a week, after the cycle is done, for the backlog of nitrite to get consumed.

So if you are anxious to finish the cycle, you should change all the water when the nitrite gets way off the chart. Then you have a clean slate and can see where things stand after a fresh dose of ammonia.

[daffers1986]

Ok, good to know it will finish still.

A bit more info as I have retested with a ‘better’ test kit.

So I started yesterday on 0 ammonia and 0.5 nitrite. Dosed with 2ppm yesterday.

Today dosed with 3ppm. Thought given the low nitrite count this wouldnt be an issue.

Have retested and I have 0.1ppm ammonia and 30ppm nitrite. I can’t see how that could even be possible. But I had to go all the way down to 0.1ml tank to 4.9ml tap just to get a reading on the scale. Nitrates 80ppm but we’ll aware that’s probably because of the nitrite reading.

I’m going to have to do a full water change. But does anyone have any insight in to what the hell is going on?

[DJW]

I wouldn't try very hard to get accurate numbers, the nitrite color card is difficult to interpret. Its enough to know its very high. If the filter really did consume 5 ppm ammonia, that would make about 13 ppm of nitrite, some of which might have already become nitrate. When I was doing cycling experiments, I found the nitrite color card was so hard to use that I made my own using known concentrations of sodium nitrite (with all the proper stoichiometry into account) and even then it was not that useful.

You are in that stage where you can cut way down on the ammonia feeding. I would dose 1 ppm per day, that way the nitrite won't accumulate so fast. You can simulate a fully stocked tank with 1.5-2.0 ppm per day ammonia anyway.

[daffers1986]

Thanks DJW, you’ve been great.

One last question. Is it ok to dose every 24hours given how quick the ammonia is consumed or should I stagger it to ensure a supply over a longer period.

[DJW]

The bacteria seem to be able to fast for a day without a problem.

[CammieTime]

I've done lots of testing in a fishless test tank on fishless cycling. The bacteria can go a couple of days without ammonia added - they don't die. To get fresh results I do a full water change on the tank to see where parameters stand.

[JamesW]

Do a full WC then dose 1ppm Ammonia and wait until your nitrite goes back down to 0. Your ammonia eating bacteria won't die off and you aren't beating the nitrite eating bacteria over the head with 30ppm nitrite. Once your nitrite bacteria consume the nitrite back to 0 then dose 2ppm ammonia and wait until both are back to 0. Constantly feeding ammonia when the nitrite eating bacteria can't handle it is short circuiting your cycle.