How long will my bacteria be ok in a tank with no fish?

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Hopeless Romantic
Original poster
Nov 7, 2002
We have a 55 gal, that is done cycling, but the fish had some ich (probly due to the fact that it was still cycling at the time)

the fish are in a smaller (easier to medicate) tank right now, they have been for 3-4 days... will my bacteria be ok? or will we risk haveing another mini-cycle?

there's a ton of plants, and some snails in there too...



Senile Member
Jun 11, 2002
new haven ct.
your risking it......... the bacteria need something to eat.

you quarantined the fish for ich? after they were in the tank? totally useless pretty much. the ich inhabit the substrate also..... the whole tank needs to be dealt with somehow. cure the fish and replace them in the tank and you will get them reinfected by whats in the tank unless you have killed it in there somehow too.

good luck


the original legend
Jan 13, 2002
Real Name
no inverts cant get ick.

boost the temp in the tank to 85 and all the ick will die within 3 days.


AC Members
James, slipknottin's got the right drill. The swarmers-- "tomites" --will die without a fish host. Don't medicate the tank, because any medication eliminating the parasitic ciliate, Ichthyophirius multifiliis, will also decimate harmless ciliates like Paramecium that spend their lives gobbling bacteria and green water algae etc.

You can poison bacteria, but you can't easily starve them. They just sit tight and wait for better days. Normal decay processes in the system provide enough NH3 to keep the community going, but if you're feeling sorry for them, just sprinkle a smidgen of flake feeed into the empty tank.

The thing not to do is feed them a taste of bottled ammonia.

ewok, in spite of what you often hear, there's no separate encysted or spore-like life stage for Ich in the substrate or anywhere else away from the host. Just a temperature-dependent reproducing cyst that lasts a matter of hours at aquarium temperatures. There are lots of links to veterinary college and agricultural dept. sites at under "Parasites." And some hobby sites too.


AC Members
Nov 29, 2002
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wetmanNY -- why do you suggest that one NOT use bottled ammonia to feed the biofilter while all fish are out of the tank?

I've done it (sparingly) several times in the past with no problems (i.e., I make sure that the amount of ammonia I add is converted to nitrAtes within 24 hours, and when I re-stock the tank there is no measurable NH3/4 or NO2.)

It always seemed to me to be a good way to keep a nice, strong biofilter going in a fishless tank. Maybe I overlooking something?