Spike in established tank

Ioana Sundius

I came back from the long weekend to find one of my guppies listless and motionless, at the surface of the tank. He ate when I fed them, but slower than usual. Then, he retired back to the corner of the tank.

I have a 20 Gallon tank stocked with 5 male guppies (he is a lone older one, with the 4 remaining ones added about 1 week ago). There are 3 nerites and 1 rubberlip pleco (3"), as well as an assortment of trumpet snails. It is a planted aquarium.

I ran a Nitrate test and indeed, it came back at 10ppm. On a hunch, I tested the ammonia, and there was a slight shade of green -- 0.25ppm or less. In the past, this was always clear, so now I also ran a nitrite test. This one also turned a pale purple from the usual turquoise, at 0.25ppm or less. PH is 7.6, slightly lower than usual in my fish tank (high pH has been something that has dodged me). Temperature is 78F.

There is a cannister filter installed about 2 months ago. I ran it in parallel with the Marineland biowheel I had before, for about 1 month, then ran it alone for the last month. Testing did not indicate a spike through this process. Last week, I changed the carbon layer and one of the 5 mesh layers, per instructions for carbon, and to have athicker foam. I assume the changing of 2 layers and adding the 4 guppies last week affected the cycle?! Since I have trumpet snails, I am assuming there is plenty load in my fish tank to feed a solid cycle, even if my tank was somewhat understocked. I was not expecting the guppies to generate a spike in a fish tank that has operated for most of 2 years.

So my solution tonight was to do a 30% water change, add water conditionner and some bacteria, and to switch the carbon layer with an ammonia removing layer in the canister.

Is this minispike (let's hope it stays mini) normal when one changes media in a canister filter? Anything else I can do with my struggling guppy?
 

AJSFishKeeper

All beneficial bacterias grow on all surface including carbon. Ur tank is probably just adjusting to the bacteria it lost. 0.25 ppm of ammonia and nitrite is fine for a short period of time and shouldn’t cause any problems with your fish. Just watch out for the next couple of days just in case it goes up more. You can dose some prime if you wish to detoxify ammonia/nitrite
 
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saltwater60

I ahmgree. Adjusting to the filter and media changes and increase in bioload. Monitor as mentioned above and do water changes accordingly. It should be fine.
 
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Ioana Sundius

A quick update: water tests back to normal -- no ammonia trace and no nitrite! My red guppy seems on the mend and is coming to meet my hand during feeding time again. He swims with the rest of them -- still a bit slower, but so much better!

Thought I'd share Thank you both for your responses!

Here's a picture of the red guppy (middle). He still looks pale and a bit bloated. There is some bruising on his side. It's possible he got injured somehow, although there are no meannies in the tank. Hope he will continue to improve. If you all see anything alarming, please let me know!
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