Ammonia???

[Mazdaman]

What could cause ammonia to show up in a tank?

I tested this morning and was showing somewhere between 0.25 and 0.5.
The tank has been running for 7 weeks now. Used "used" filters and water to reduce any cycle. Saw a mini cycle for 10 days and then all tested very well for the last month i guess. Other than the 25% i changed out this morning, the last pwc was last friday, it was also the first time i did a gravel vac (new substrate with tank)(only did 1/4 of the tank) and rinsed the first sponge in tank water as it was pretty clogged with "stuff". I left the ceramic rings and 3 sponges alone, but i did replace my top filter floss with "pre-soaked" new floss.
Any ideas why i would be seeing this little spike in ammonia?
Thanks for any help...

 

[megos1]

you don't really want to do a gravel vac & clean out your filters on the same day you're kind of getting rid of too much of the bacteria that was living in there and that bacteria breaks down ammonia. so basically, without them your ammonia goes up.

what do you have in there for fish/plants etc?

 

[Mazdaman]

My tank is pretty lightly stocked right now.
3 rainbowfish
6 harlequinn rasboras
5 panda cories

As I stated I only cleaned 1/4 of the tanks gravel and only rinsed out one foam filter pad. Three more foam pads were left untouched and the ceramic were left aswell. any other ideas?

 

[Jchillin]

Did you use tank water to rinse the sponge? If not, that could kill off some bacteria as well.

 

[TomK2]

Did you test the water for ammonia before or after the water change? Chloramines in the tap water could cause a temporary ammonia reading.

 

[TankGirl]

If you switched dechlorinators you might see a false positive reading also, to amend what TomK2 suggested.

Other than a false positive reading, or a spike related to the gravel vac and filter maintenance, the only other thing I can think of would be a dead fish tucked away somewhere.

 

[Mazdaman]

the dead fish was my first thought. there is one of the new panda cories that hides all the time. He's really small too so finding him was tough but he's there and slowly starting to come out more and more. I tested before the water change and again this morning. The pwc did make a difference as now it appears to be below 0.25.
But in a mature setup shouldn't there be a dead zero reading for ammonia?
I ALWAYS rinse in tank water so i don't think that did it.

One thought occured to me. I had did the maintenance early the day I added the 5 cories. Since my bio-load grew the same day I "removed" some of the bacteria, could the addition be causing a little ammonia to show up untill more bacteria grows in the filter?
Thanks for the replies...

 

[Jchillin]

To be honest, although your tank cycled, it really hadn't "matured" enough. This usually takes a month or more. I just remembered this from an experience that I had went through early on and experience a "mini-cycle" right after the tank was cycled. Your final thought seems to support this.

 

[mattrox]

Kudos for finding the source of the problem.