Tank cycling

[Doughdog]

Hello, my aquarium has been running for a good 12 weeks now and i thought it had finished cycling about a month ago as the nitrite dropped off leaving me with PH at 7.6, Ammonia 0-0.25ppm, nitrite 0ppm and Nitrate 20ppm. However in the last week and a bit the ammonia has shot up to toxic levels but the nitrite is still 0 and nitrate still at 20. I did change the carbon filter pads 1 at a time with a 2 week gap between changing over the last 4 weeks so not sure if this has kicked off a mini cycle and i should just wait it out?

I only have 2 Axolotls in the tank which i feed every other day and have been doing weekly(some times twice a week if the ammonia was particularly high) water changes around 20%.

Any advice?

Thanks,

 

[Donna001]

If the levels of ammonia are high it would be worth removing your axolotls and putting them in smaller containers with daily 100% water changes whilst your tank stabilises.
Over vigorous cleaning of filters, or changing pads close together, can cause a mini cycle. If you change the pads 2 weeks apart the filter may not have had enough time to build up the levels of bacteria before you changed the second pad.
I could be wrong, and I've only been keeping axolotls since the end of February, so perhaps one of the more experienced keepers will give you more specific advice.
Best of luck.

 

[ohaxies]

The higher the PH you have the more toxic ammonia is, even at lower levels. We learned this the hard way when we changed the filters out in the 125 cichlid aquarium, it sparked a mini cycle and then everything shot up and we lost half the tank. If you can't get it down then remove the axolotls. If you have another tank that is cycled then you can use filter media from that to help your tank cycle easier. I used old filter media from my 55 and my 75 was cycled in a week.

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