Fishless Cycling Hiccup?

[Irf]

Hi everyone....

First of all, I know I'm not a total beginner and I've been through this before - but I just can't answer the questions I've been asked!

My sister has been drawn into our world of fishkeeping (yay!), and she's been cycling for about 3 weeks now. The tank is about 70L (2ft) I believe.

The cycling was all going as it should, until last week when she did a couple of things that might have broken things. She was at the point where the ammonia was going down slowly, and she was topping it up, and the nitrite was spiking.

She reduced the temp from around 30C to 26C (because she read that most fish like to be around that figure) - even though she doesn't actually have fish yet! She also added water to compensate for the loss through evaporation.

After these actions, the ammonia level stopped dead at 2ppm - it didn't shift for almost 5 days. She got impatient and added a bit more ammonia to bring it back up to 5ppm. It has stayed at that same level for 3 days. The nitrite is still off the scale.

Any ideas on what may have happened? Apparently the water was dechlored (using some left over stuff that came with the second-hand tank she bought). I was suspicious of the dechlor she may have used, but assuming it was not OK would the raw tap water with Chlorine wipe out the bacteria?

Thanks for any help.

Irf.

 

[mark.w.jones]

I would say the water dilution with possibly dodgy dechlorinator and temperature drop are what has caused the problem, unless there is some kind of blockage in your filter. Changing these things have caused some bacteria to die back. They are sensitive little things these bacteria. Tell her to raise her temperature back up to 30 and just to persevere. Eventually the ammonia will begin dropping to 0ppm in 24 hours. Does she have any live plants? As again these can really slow things down. The only other thing is whether her test kit is a bit ropey.

 

[rdd1952]

Definitely raise the temperature back up. Once she's finished and does the big water change, she can adjust the temperature back to where it needs to be. Lowering the temp shouldn not have stoped the cycling though. Slowed it a little maybe but not stopped.

The only reason I can figure for the cycle stopping is if the dechlorinator didn't work. Has she checked the nitrates to see if they are rising? If they are, then the nitrite is being processed so at least that bacteria is still ok.

Some people have had luck getting things going again with a water change of about 50%. There's no reason that should work but it seems to have helped some people. Just check the dechlorinator to make sure it is good.