Cycling a cold water tank

[Wulfonce]

I have a new 53 gallon corner tank (curved front, 90 degree back). It's intended purpose is to house a 10" goldfish that I've had for almost 12 years. I'm currently in the stages of cycling the new filter, but I'm having some trouble.

The following method I've done almost 10 times and it works every time.

I raise the ammonia level to around 5ppm using 100% pure ammonia. Then I stick a bit of already established filter media in the new filter, and usually within 5 days, the ammonia levels are back down to 0ppm. Now 2 weeks later the ammonia is still at 5ppm and I never got the milky white bacterial bloom that I'm use to seeing. Is this temperature related? When I normally cycle a tank its around 78F, this tank, due to not having a heater, is around 68F. I'm more then willing to buy a new heater if its needed, and I'll probably buy one anyways for the fishes sake (he'd probably like 75F a lot better then 68F?)

But that aside, I'm really curious as to why the tank isn't cycling. I've been fish keeping for over 15 years and have never had a cold water tank, nor have I ever seen a tank not cycle using the above method.

 

[esoxlucius]

I suspect it is a temperature thing. There is a goldilocks temperature band where bacteria grows best. Either side of the goldilocks band and bacterial growth decreases. I'm looking at setting up a cold water system for our native european perch in the next couple of years and rather than go through what you're experiencing now i'd probably have the temperature set at the bottom end of the tropical spectrum, maybe more, so the fish wont be too uncomfortable and i can still benefit from good bacteria growth. If you look on any sites at the nitrogen cycle they usually give all the temperature ranges and ph ranges for best bacteria growth. And in any case, like you said, your goldfish should still be ok at a higher temperature anyway.

 

[predatorkeeper87]

I cycled my NA native tank at like 65 degrees, took about 5 days with seachem stability and all the fish added day 1, I know there is a temp line as mentioned above but I had no issues.

 

[Drstrangelove]

This is an interesting question. At 20 C, you are only getting around 40% of the maximum efficiency (assuming pH is also at the peak point.)

I would lower the ammonia amount. Half the amount perhaps.

The lower temperature will reduce the ability of the BB to process the ammonia and nitrites, but it won't protect the BB from ammonia or nitrite inhibition. BB aren't impervious to ammonia and nitrite. BB will be inhibited by 10 ppm of free ammonia, so your levels, while lower are likely reducing it's ability to process along with the temperature. (10 mg/l for Nitrosomonas; 0.1 mg/l for Nitrobacter)

This isn't a certainty, but it makes sense since the recommended levels for fishless cycling is lower (3 ppm), and the temperatures are higher (77-86 F.)

You might need to try a new piece of mature media, but for now I think you still have BB in the tank, but it's not very active.

 

[duanes]

I worked at a water supply plant, and we tested the biofilm in the distribution system for bacterial species, because we disinfected with chloramine.
The biofilm contained a plethora of ammonia and nitrite consumminers, water temps averaged between 37 and 55'F most of the year.

 

[Wulfonce]

Interesting stuff.

I bought a heater today. I'll try bumping it up to 82F and see if anything happens. I lowered the ammonia to 3ppm as well.

 

[Wulfonce]

Update: The tank cycled once I bumped the temp up. All is well now.