How Long Does A Cycled Tank Stay Cycled If There Are No Fish

[Yoshi'sdad]

Hi I have another question. I may sell my frontosa out of my 125 gallon tank and want to replace the cichlid sand with gravel. I am wondering if I remove the sand and keep the canister filter running and the 3 aqua clear filters running, how long will the tank stay cycled? The existing rocks will stay so there will be bacteria in the filters an on the rocks and the aquarium walls. I am thinking tank full of rainbow fish, different varieties.

thanks
Yoshis dad

 

[celaeno]

fish provide the beneficial bacteria in the filter with food in the form of ammonia from their waste. if there are no fish, there's no ammonia, so as soon as you take the fish out, the bacteria in the filter start dying after 5-15 mins.

 

[Yoshi'sdad]

wow I thought it would 12 hours or so, could i put in some raw shrimp or something to keep them going until I add fish

 

[celaeno]

what you can do is buy some pure ammonia (you can get it in walmart if you're in the usa) and add a small amount to the tank water every few hours.

you can use a medicine dropper or cup to measure the amount needed. just don't overdose or underdose, or bacteria will start dying off.

make sure to keep the filter running even when there are no fish in the tank.

 

[Mikaila31]

I disagree that the bacteria will start dying in 5-15 minuets. It will still be processing the ammonia left by the fish IMO. In my experience if you let a tank sit for about 2 hrs tops without fish, you can add the same bioload back to the tank without a problem. But that is pushing it, I don't like to leave the tanks for more than an hour and a half without fish. Add back the same bioload or less, don't increase the bioload. Let the tank sit 2 weeks before adding more fish.

 

[billy0510]

I have moved my 125 gal tank three times. the first two times the tank was down for about 3-4 hours, I just keeped the fish i the old water in (5) 5 gal buckets and keeped my filters full of water. I used the old water for my new setup and my tank had a slight ammonia spike nothing major. 12 hours not sure but you might be pushin it. Can you get some zebra danios (they dont cost to much) even if u return them and dont get your money back it will still be worth not losing your bio load.

 

[Bignose]

You guys are way underestimating it. Assuming the filter stays wet, the bacteria will be okay for actually about 24 hours. What happens is that some of the bacteria starts to die, it decomposes, one of the products of that decomposition is ammonia, and the rest of the colony can live off that for a fair amount of time.

5-15 minutes is just a ridiculously short amount of time. The filter bacteria are actually among the slowest in the bacterial world. They take a long time to grow and, in exactly the same way, they take a long time to die.

All that said, a big ol' jug of ammonia is only a dollar or two, and it does seem silly not to buy a jug if you plan on leaving the filter without fish for any significant amount of time.

 

[rust81]

You guys are way underestimating it. Assuming the filter stays wet, the bacteria will be okay for actually about 24 hours. What happens is that some of the bacteria starts to die, it decomposes, one of the products of that decomposition is ammonia, and the rest of the colony can live off that for a fair amount of time.

5-15 minutes is just a ridiculously short amount of time. The filter bacteria are actually among the slowest in the bacterial world. They take a long time to grow and, in exactly the same way, they take a long time to die.

All that said, a big ol' jug of ammonia is only a dollar or two, and it does seem silly not to buy a jug if you plan on leaving the filter without fish for any significant amount of time.

I agree. I had a power cut last Friday that meant my filter turned off and didnt re-start properly. By the time i got home the filter had not been on for about 9 hours, although it was obviously still full of tank water. I restarted it and tested the levels - no spikes whatsoever

 

[Yoshi'sdad]

You guys are way underestimating it. Assuming the filter stays wet, the bacteria will be okay for actually about 24 hours. What happens is that some of the bacteria starts to die, it decomposes, one of the products of that decomposition is ammonia, and the rest of the colony can live off that for a fair amount of time.

5-15 minutes is just a ridiculously short amount of time. The filter bacteria are actually among the slowest in the bacterial world. They take a long time to grow and, in exactly the same way, they take a long time to die.

All that said, a big ol' jug of ammonia is only a dollar or two, and it does seem silly not to buy a jug if you plan on leaving the filter without fish for any significant amount of time.

thanks, my concern is I will be going from 14 inch fish to 1-3 inch fish. I am sure that some bacteria will die when I introduce some fish because the load will be so different, but am hoping that if I can 10 rainbow fish, maximum size 2 inches, it will be enough to keep the tank established while I slowly stock it with tropicals. I don't want to run to the store 15 minutes after the frontosa are gone and buy 40 tropical fish. I want to take my time and select fish that are compatible and will make a nice showcase.

I have extra bio balls sitting in my 220 tank that I will transfer as I add more fish. I just want to avoid the 6 week cycling event if I possibly can.
Yoshi's dad

 

[the biffster]

i have 14 tanks and have been Thur some long power cuts 48 hours one was
when the power came back on it all started back up and everything was back up to temp
in a few hours week later tested the water no ammonia spikes of any sort the fish room is heated
by a gas fire so no probs with keeping it warm but no damage done oh by the way also no air pumps
and still all OK once ran a five foot by two by two for six months with a small stocking level and weekly
water changes with no problems its hard work but it can be done

any good luck biff

 

[Bignose]

Take a look at this document:

http/cobweb.ecn.purdue.edu/~alleman/w3-a...r-behavior.html

Specifically the section about half way down called "Nitrifier Death and Decay"

The author says that their best estimates are that the colony will experience somewhere between 5 and 12% death per day when they are starved.

Also note how the author considers this a benefit, since "They can be shifted (e.g., taken off-line) into a dormant or resting state for extended periods with less concern about retaining their viability." Meaning, like I said above, and in concert with the anecdotes that were presented, a tank can be left without an ammonia source for a fair amount of time.