What can harm a cycle?

[Masha]

Educating myself while I'm waiting for my tank to cycle (I was SO SURE it was cycled, but still getting a bit of ammonia 24 hours later. Nitrites 0 now so I have hope...)

Once a tank is cycled and up and running for a while: what might harm the beneficial bacteria in a tank, or cause a tank to stop being cycled?

I can guess switching the filter off, adding certain medications, maybe?
Would a clogged up filter with very little water going through, become "uncycled"?

Cleaning the filter too vigorously?

 

[NewToFish1989]

My experience, rinsing things under tap water such as the filter sponse and sticking it back in the tank kills the good bacteria.

 

[Samzter]

If the pH is too low it could stall the cycle. Or possibly if it's too cold. Not sure on the last one

 

[BBradbury]

Tank Bacteria

Educating myself while I'm waiting for my tank to cycle (I was SO SURE it was cycled, but still getting a bit of ammonia 24 hours later. Nitrites 0 now so I have hope...)

Once a tank is cycled and up and running for a while: what might harm the beneficial bacteria in a tank, or cause a tank to stop being cycled?

I can guess switching the filter off, adding certain medications, maybe?
Would a clogged up filter with very little water going through, become "uncycled"?

Cleaning the filter too vigorously?

Hello Masha...

Good bacteria grows on all the surfaces inside the tank, so if the bacteria that lives in the filter media was lost, your tank would still be safe for the fish. Bacteria that's removed when the filtration system is cleaned reproduces very quickly and replenishes what's lost in a few hours.

Oxygen is important to the life of the good bacteria and turning off the filter would reduce the oxygen that gets mixed with the tank water, but that would take many hours.

Medications are rarely, if ever the answer to tank problems. Large, weekly water changes will prevent most, if not all tank problems, so there's really no reason to use meds. They can negatively affect aquatic plants, fish and the good bacteria.

Just one reporter's opinion, though.

B

 

[Masha]

Fantastic- thanks for all the answers

 

[jlk]

Just thought I would add a bit here as its a great question! Not using water conditioner is a big one as it may result in dead fish as well as dead bacteria.

Meds are an obvious one as well- antibiotics do not discriminate between 'good' and 'bad' bacteria. Methylene blue (some ich products contain MB) is a cycle killer as is potassium permanganate. Certain other meds may or may not affect a cycled tank- it depends on various factors including (but not limited to) ph, gh, kh, how well established the tank is, etc. Salt will affect a fw cycled tank but it's dosage dependent.

Your bacteria are very oxygen and ph dependent as well as temperature dependent. Extreme high temps will kill them (but your fish as well) but also keep in mind lower to low temps affect them to an even greater degree. Their efficiency and activity is reduced dramatically as the temp drops and they die once the temps hit about 40. Hope this helps a bit!

 

[Masha]

Excellent, it does!

 

[Cactuspixie]

Also too much ammonia can stall a cycle.