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Hi all,

I put a HOB filter on the back of my already established 75g tank. I want to use the HOB on my 25gallon tank.

How many days will it take for the HOB to build up enough beneficial bacteria so I can put it on my 25gallon tank?

By the way, the HOB is a Emperor 400.

Thanks,
pdub
 

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The best way in my experience is to take some filter media from a running filter and put it in the new one (or just wring it out into the new filter if you grab a sponge from the running one). Then you can start adding fish right away.
 

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Chris 2500DK, I think the question I was trying to answer is, when you take the filter off the established tank...how long should it have been ON the established tank. Like you would not want to change all the filter media on the established tank today, and move it to the new tank tomorrow.

TheeMon, my two weeks is from reading all posts on this forum since I joined. Usually the "facts" that stick with me are from a mod or a very experienced poster, and I've seen this more than once, but can't cite the actual post. If you think about how long it takes the bacteria to grow during a cycle...
1-from the time when you first start getting nitrite (which means a few bacteria have latched onto the filter and are eating ammonia and creating nitrite waste)
2-to the time when the ammonia goes to zero (which means enough bacteria have grown to eat all the ammonia produced by the fish)

Thats about a week (I still have the daily log of readings from the cycle on my first tank).

If you allow a couple of days at the beginning for the bacteria to find and latch onto the filter, and a couple of days at the end to be safe...two weeks just makes sense...to me anyway, LOL.

I've never tried something shorter, and I've cycled all my tanks from the original using the two week timeframe. But the two weeks is not something I've proven is the minimum by trying shorter periods until failure occurs, or examining the filter with a microscope. So, given my signature, I should have said "IME, two weeks." :thumb:
 

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I ran my new filter on an established tank for 3 week. (only because it took that long to get the other tank and get it all set up) My new tank has two filters. I did filter squeezes to the second filter that was not run in my other tank. I then added 4ppm pure ammonia. It took me exactly 11 days until my tank was fully cycled and ready for fish.
 

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How come it took an additional 11 days and more ammonia to completely cycle your tank? IME when you let the filter run on existing tank for 2 weeks there is no cycle in the new tank because you are adding a completely mature crop of bacteria that can 100% support the fish load.

Of course, the fish load in the established tank would need to match or exceed the fish load in the new tank.
 

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The new filter was running in a 30 gallon and my new tank was 75 gallon. I can only think that was the reason. Actually, the people who talked me through cycling were surprised it took so long also. It sounds like the poster here is doing it the other way around (running in larger tank to add to smaller tank) so most likely theirs will go much faster.
 

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Huh. My first tank that went through the only cycle I've ever done was a 10G. I used the 10G filter and 50% of the substrate to to establish a 38G with the same fishload and never had a hint of ammonia. Then a year later I used the established 38G provide bacteria for the 125G with the same fishload. No ammonia.

The only time I've ever had ammonia was one time I moved an established filter from a 10G to set up a "new" a 20G quarantine. I had changed the cartridge a week earlier, and I had an unexpected and powerful ammonia and nitrite spike.

IMO the extra week helps, but cannot prove it.
 

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My 30 gallon had mostly neon tetras in it at the time. I really have no idea why it took so long. It was the fist tank I ever cycled (the 75 gallon). I had no clue what I was doing when I started the 30 gallon. I just added water and fish on the same day. I lost a bunch of fish and learned to start reading and asking for advice. When I set up my 10 gallon, I just put a sponge in an extra media slot in my 75 gallon for 2 weeks and it was good to go the day I added it to the 10 gallon.
 
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