What On Earth Is Up With My Cycle?

ivyninja

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Have been cycling my tank (45 litre/12 gallon) for 5 weeks now. For the last 2-3 weeks ammonia is 0 after 24 hours, I am getting nitrate readings but nitrites are staying sky high.

I have been doing water changes to keep the nitrites in check but doesn’t seem to make a difference, by the next day they are off the charts again. Is that normal in this point in the cycle? I feel like I must be doing something wrong or missing something, but in that case my ammonia eating bacteria wouldn’t be doing such a good job, would they?

Yesterday I did a 90-95% water change then dosed to 1.5ppm ammonia. Tonight ammonia is 0, nitrites are 2-5ppm, and nitrates are 10-20ppm. The numbers don’t seem to add up?

I didn’t initially use bottled bacteria, but added some on the weekend on my husbands insistence (he’s fed up of waiting), hasn’t made any difference so far.

pH is 6.6 or higher (I’ve got crushed coral in there which brings it up slightly but it does drop back for a couple of days after a large water change). I haven’t messed with my filter sponges other than to very carefully wash off (in tank water) some slimy gunk that accumulated around where the intake vent sits, I’m using water conditioner/dechlorinator at the recommended dosage, I’ve got a few live plants in there, lights on 8 hours a day and heater set to 25C (77F).

Do I just keep waiting? My nitrite and nitrate levels don’t seem to correspond with the amount of ammonia I’m adding - is that normal?
 

Heron

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It's just the phase of cycling your in. The bacteria that convert nitrites to nitrates only start to multiply once the bacteria that convert ammonia to nitrites have bloomed. BB products should contain both bacteria so it should just be a case of waiting for them to grow. I assume as you say that you are dossing ammonia that this is a fish less cycle. In which case I wouldn't do any water changes until ammonia and nitrites are 0. Then you will likely have sky high nitrates, this is the time to do large water changes to get nitrates down to 5-10 before adding fish.
 

Zigi Zig

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Hello
Since you have new tank there is limited bacteria in the filter. Only about 10-15% water should be changed, any more and you will be taking away the ammonia and nitrite that the bacteria are trying to feed on. Your water changes has to be done slowly if is done quickly or in large quantity will spike ammonia levels and result in a mini-cycle.
 

Skavatar

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usually the ammonia phase lasts 3 week and the nitrite phase lasts 3 weeks. you said you're on week 5, so about another week to go. and yes nitrite levels will be sky high, b/c 1 ammonia molecule gets converted into 3 nitrite molecules.
 

mattgirl

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It isn't unusual to have high nitrites one day and zero the next. I can already see you doing the happy dance when that happens.

When I was doing my fish in cycle and the nitrites spiked I was doing daily water changes. I did that 5 days in a row. Each time the nitrites were registering off the chart. After the 5th day the nitrites dropped all the way to zero. So it seemed like they instantly went from off the chart to zero over night. I have seen it happen this way for other folks too so hang in there. I have a feeling you are almost there.

Since this is a fishless cycle you can hold off on the water changes. The high nitrites aren't going to stall your cycle. The only time I have seen that happen is when both nitrites and nitrates are way off the chart. When that happen the cycle stops or slows the ammonia eating bacteria down. Since your ammonia continues to go down to 0 within 24 hours your cycle is moving forward.

You low PH may be slowing things down a little bit. Have you tried adding more crushed coral to get it up a bit higher?
 

Momgoose56

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The nitrobacter (nitrite oxidizing bacteria) take almost twice as long to replicate as the nitrosomonas (ammonia oxidizing bacteria) so if it took three weeks from the time your ammonia started dropping until it stayed at 0ppm, then it will take about 5-6 weeks from the time your nitrites started dropping (or didn't rise despite ammonia dropping) until they drop to, and stay at 0ppm. What bacteria (brand) did you use?
 
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ivyninja

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Thanks all. It appears I was worried unnecessarily - a couple of days later, my tank was cycled!

The nitrobacter (nitrite oxidizing bacteria) take almost twice as long to replicate as the nitrosomonas (ammonia oxidizing bacteria) so if it took three weeks from the time your ammonia started dropping until it stayed at 0ppm, then it will take about 5-6 weeks from the time your nitrites started dropping (or didn't rise despite ammonia dropping) until they drop to, and stay at 0ppm. What bacteria (brand) did you use?
You were right, the ammonia took about two weeks to start dropping, and the nitrites took four, so a total of six weeks.
 

Momgoose56

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Thanks all. It appears I was worried unnecessarily - a couple of days later, my tank was cycled!
You were right, the ammonia took about two weeks to start dropping, and the nitrites took four, so a total of six weeks.
Congrats! What bacteria did you use? Just curious, it seemed to really speed things up!
 
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