Rising ammonia in fishless cycling...

[Mud puppy]

Why would ammonia rise from 2ppm to 4ppm overnight during a fishless cycle? I'm helping a friend cycle her tank and she dosed her tank to 2 ppm ammonia and the next day it looked 4+ppm ammonia. Nitrites and nitrates are showing so its processing some but the ammonia isn't dropping. After a few days we did a partial water change just to get the ammonia back to a reasonable range and didn't dose any ammonia but the next day it was back up to 4+ppm. I've done fishless cycle in 4 tanks in 2-3 weeks and never have seen this issue. Can someone explain how the ammonia could rise without dosing during a fishless cycle?

 

[Colin_T]

How long after adding the ammonia did they test the water for ammonia?
eg: if they added ammonia and tested straight away, they might have gotten a diluted sample of water. A few hours later the ammonia would be evenly distributed throughout the aquarium and the level might be higher.

Alternatively the first test was faulty/ contaminated or something has decomposed in the tank during that time.

Make sure test phials are rinsed out well straight after use.

 

[Mud puppy]

Water was tested 1 hr after adding ammonia to a 20 gallon long. Also when ammonia got 4+ppm and wasn't processing a 25% water change was done which brought ammonia to 2ppm the next day it was back up to 4+ppm. Tap water was tested and no ammonia was present.

 

[Aiken Drum]

Its probably coming out of something in the aquarium like the substrate or driftwood. If you have plants in the tank maybe the plants dying and the decay is an ammonia source. More details on whats in the tank please.

Try taking some of the substrate and putting it a small container of water overnight and see if you detect any ammonia.

 

[Mud puppy]

Drift wood and java fern with no substrate...could a dying plant really increase the ammonia by 2ppm?

 

[Aiken Drum]

Could do yes, depending on how much decaying plant matter there is.

Try removing the driftwood and see if that helps. If you can put the driftwood into a container of water and if ammonia rises in the container too.

 

[Mud puppy]

Ok we'll try that...thank you for the suggestion!