Ammonia Processing Rate Different After Water Change

This is my third nitrogen cycle post in 3 days, you all are probably getting annoyed by now. So I’ve been fishless cycling my tank for around 36 days. Yesterday my tank had processed 4.0ppm of ammonia in 24 hours, and my nitrites were zero after about 28 hours. My nitrates were extremely high so I performed a 100% water change, and redosed 4.0ppm of ammonia like I have been my whole cycle, but today when I tested my tank 24 hours after adding the ammonia yesterday my tank hadn’t processed hardly any of the ammonia. Here’s my results:

June 19th, 2:00pm

pH - 7.6
Ammonia - 0ppm
Nitrites - 0ppm
Nitrates - 80ppm
After testing I added 4.0ppm of ammonia

June 20th, 2:00pm

pH - 7.6
Ammonia - 0ppm
Nitrites - 0.25ppm (dropped to 0 four hours later)
Nitrates - Over 100ppm
Performed a 100% water change to lower nitrates, and then added 4.0ppm of ammonia

June 21st (today), 2:00pm

pH - 7.6
Ammonia - 4.0ppm
Nitrites - 0ppm
Nitrates - 10ppm

So you can see my tank was processing 4.0ppm of ammonia in 24 hours, and after the 100% water change doesn’t seem to be. Can anyone explain this to me? If I messed my cycle up I am going to be severely bummed. Sorry for all the questions everyday, I’m just trying to learn and get everything right. Thanks!

 

This is strange. I wouldn't have changed out 100% of the water but even so I can't imagine doing so would have caused to tank to stop processing ammonia. Right now I would just give it a bit of time to get going again.

Can you tell us exactly how you did the water change? Did your rinse media, allow substrate/ decor to dry out. Did you temp match and use your dechlorinater in the new water?

 

This is strange. I wouldn't have changed out 100% of the water but even so I can't imagine doing so would have caused to tank to stop processing ammonia. Right now I would just give it a bit of time to get going again.

Can you tell us exactly how you did the water change? Did your rinse media, allow substrate/ decor to dry out. Did you temp match and use your dechlorinater in the new water?

I turned my heater, pump, and lights off, let the tank sit for around 20 minutes. Removed all the tanks water, probably 13 gallons. Did not remove or rinse any substrate or decor, also didn’t do anything to any of the filtration or filter media. Filled buckets with temperature matched water less than 1 degree Fahrenheit difference of the tanks water, treated each bucket with Seachem prime, added the water to the tank. Plugged everything back in after about 10 minutes of adding all the water. Then dosed my tank with 4.0ppm of ammonia.

 

I turned my heater, pump, and lights off, let the tank sit for around 20 minutes. Removed all the tanks water, probably 13 gallons. Did not remove or rinse any substrate or decor, also didn’t do anything to any of the filtration or filter media. Filled buckets with temperature matched water less than 1 degree Fahrenheit difference of the tanks water, treated each bucket with Seachem prime, added the water to the tank. Plugged everything back in after about 10 minutes of adding all the water. Then dosed my tank with 4.0ppm of ammonia.

Your bacteria shouldn't have been affected so I don't think I would panic just yet. Test again tomorrow and we have to hope the ammonia will be down by then.

 

Your bacteria shouldn't have been affected so I don't think I would panic just yet. Test again tomorrow and we have to hope the ammonia will be down by then.

Okay will do! The only reason I did a 100% water change is because during the cycle I had done a few 75% water changes which only brought my nitrates down to somewhere around 80. So I figured since my cycle was nearly complete and my nitrates were still high that I should do a 100% water change since the 75% wasn’t cutting it. But right now it’s looking like that might have been a mistake, but hopefully not.

 

How fast did you refill the tank?

I wouldn't be too surprised if the bacteria are sensitive to pH change/osmotic stress.

 

How fast did you refill the tank?

I wouldn't be too surprised if the bacteria are sensitive to pH change/osmotic stress.

After emptying the tank I started refilling the tank within 10 minutes and the tank was completely filled within 25 minutes.

 

After emptying the tank I started refilling the tank within 10 minutes and the tank was completely filled within 25 minutes.

That might've done it.

A quick search found an article on how osmotic stress caused a sudden 70% drop in nitrifier performance so the idea that the bacteria can be upset isn't too crazy.

 

That might've done it.

A quick search found an article on how osmotic stress caused a sudden 70% drop in nitrifier performance so the idea that the bacteria can be upset isn't too crazy.

So has my cycle stopped? And will I have to restart from the beginning? Thanks for the info.

 

So has my cycle stopped? And will I have to restart from the beginning? Thanks for the info.

They're probably not dead, just diverted their resources to repair and reestablishing homeostasis. There's a good chance they'll bounce back after a few days.

 

They're probably not dead, just diverted their resources to repair and reestablishing homeostasis. There's a good chance they'll bounce back after a few days.

Okay I hope that’s the case! Not sure my wife will be too excited about a fishless fish tank sitting in our living room for another month. Do you know if there is a typical time frame for the bacteria to repair and reestablish? Should I just test my water every 24 hours or sooner than that?

 

Okay I hope that’s the case! Not sure my wife will be too excited about a fishless fish tank sitting in our living room for another month. Do you know if there is a typical time frame for the bacteria to repair and reestablish? Should I just test my water every 24 hours or sooner than that?

I would just test every 24 hours. It almost certainly won't take as long as starting from scratch. Hopefully, just a few days.

 

I would just test every 24 hours. It almost certainly won't take as long as starting from scratch. Hopefully, just a few days.

Okay thanks for the help!

 

Any progress that you made please? Im also somewhat in same situation wherein ammonia processing was happening to 0 however nitrites were off the scale. Post changing water it is somewhat stalled and now waiting for nitrites to appear
Ammonia still not cycling to zero

 

Any progress that you made please? Im also somewhat in same situation wherein ammonia processing was happening to 0 however nitrites were off the scale. Post changing water it is somewhat stalled and now waiting for nitrites to appear
Ammonia still not cycling to zero

Is your pH high enough? Over 7? Ideal pH for nitrifying bacteria is ~7.8.

 

Here is my dilemma:-https://www.fishlore.com/aquariumfishforum/threads/fishless-cycle-dilemma-stalled.463164/