[lowrez]

I've got an established 55 gallon and I need to downsize into a 40 because of space. The old tank is under stocked and I'm pretty sure everyone will do fine in the new tank. I have a canister filter on the 55 that will eventually be moving to the 40. I had an old HOB that I ran on the 55 for a month before setting up the new tank and the 40 gallon has been up and running for a few weeks. I wanted to get the new CO2 figured out before I started moving fish in, everything seems good and I'm ready to start transferring. I've been adding ammonia and checking the parameters on the new tank, and now I've finally started to register Nitrites. So I'm pretty close to finishing the cycle.

Should I continue to cycle the new tank with the HOB and when done slowly move the fish over a few at a time until about half of the fish are in the new tank and then swap the filters or just move the canister and all the fish over at once? If I do move everyone over at once is it important to finish the cycle or just do a big water change and swap filters?

 

[bsmith]

I would move over the smaller fish, a couple a day then after a week or so move the larger ones and have all of the fauna from the old tank moved to the new one by two weeks. There should be enough bio activity in the new tank and filter to be able to handle the load till the filter from the old tank is moved over when the last of the fish are moved (if that's how I'm reading you are planning on utilizing the filters).

 

[nalu86]

move your fish and canister filter at the same time, canister filter is cycled, so tank is instant cycled.

 

[bsmith]

move your fish and canister filter at the same time, canister filter is cycled, so tank is instant cycled.

This is not true. It's been a long time that this misconception has been floating around our hobby. Nitrifying bacteria is much more fragile in the fact that it can only live as long as there is food (ammonia) for it to thrive on. When this food source is depleted the colonies can actually due off with in 48 hours.

In this case I think the op would be fine doing as you suggested but for the overall safety of the fish/bio system it us best to transition slowly so the colonies can grow in correlation to the load that the fish put on it.

 

[nalu86]

This is not true. It's been a long time that this misconception has been floating around our hobby. Nitrifying bacteria is much more fragile in the fact that it can only live as long as there is food (ammonia) for it to thrive on. When this food source is depleted the colonies can actually due off with in 48 hours.

In this case I think the op would be fine doing as you suggested but for the overall safety of the fish/bio system it us best to transition slowly so the colonies can grow in correlation to the load that the fish put on it.

Yes, In this case, I read all the facts really careful, and made my statement this way. I would never recommend to use an established filter to a dead aquarium (or not alive water). But in this case, he already added ammonia for a longer time and he already saw the Cycle started ( I don't really remember but think it was Nitrite (don't feel like rereading because I know I was wright and now I have to defend myself...))

 

[Kathyy]

The canister is on the 55 with the fish and holding a good colony of bacteria, the 40 is being cycled with ammonia so it has a good colony as well. I agree with nalu86, move the canister and the fish over at the same time and keep the HOB going as well for a couple days just in case.

There isn't any filter running without a food supply in this case.

 

[wetworks]

Almost any filter that has been running for a while has enough of a buildup of organic debris in the cracks and crannies of the filter to support the needs of the nitrifying bacteria for at least a short time. One thing to keep in mind is that nitrifying bacteria colonies grow in direct proportion to the food source (organic waste) that is available to them. I think that how you do it depends on how big the bioload is; in other words, how many fish are there. If the tank is understocked, then it might be safe to move them all at once, depending on the individual needs of each fish. Tetras, for instance, are typically very hardy and can stand ammonia/nitrite/nitrate levels that, say, otocinclus catfish could not. If you are not sure, and you have the time and patience, err on the side of caution and move them slowly, as bsmith suggested, and you will probably be just fine.

 

[lowrez]

Checking in, I moved my school of Cardinals and a SAE over today. If all goes well, I'll move over the Bolivian Rams in a few days. Then swap the filters and move the Rainbows and Corys over next weekend.

Thanks for the advice!

 

[kalawai2000]

I really enjoyed this thread....