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I've never done this before, and was just wondering if anyone else has tried it and had any success.

I'm setting up a 25 gallon aquarium for my Corys in about two weeks.
I need to upgrade my filter, and have a friend who's willing to sell me one of his MarineLand filters. His tanks are very well kept, and he's been keeping freshwater and saltwater tanks for years with lots of success. He asked if I want it left cycling in the aquarium it's currently in until I get my aquarium set up and filled. My question is, is it safe to use a pre-cycled filter from a well-established tank, for a brand new aquarium? I was thinking of the benefit of having bacteria ready to go rather than starting from scratch, but I've never done this and wasn't sure if it's too risky for my own fish.

Thoughts?

It's only risky for your fish if his tank has disease. So if you're getting all new fish which are not guaranteed disease-free and in a tank by themselves (ie, not from a LFS), you're not running any more risk than if you're starting a new filter. However, you get to skip the cycle and not have to worry ammonia poisoning for your new fish with an established filter (or just the filter bio media).

I agree.

My own fish will be going in there.
I have a smaller tank with some fish I've had for a couple years. I want to set up my 25 gallon for them. As far as I know, nothing's wrong with his aquarium. I don't think he'd sell me a filter that's in a tank with any sickness either...

I liked the benefit of already established bacteria, as I don't have a lot of time to get the 25 going. I just wasn't sure if there were any kind of risks involved.

So, if I decide to go through with it and move the entire filter with media into my tank with new water, is there anything else I should do to make sure it's good to go before the fish move in?

One thing you might want to do is clean it (the tubes, impellers, etc.) to make sure it'll run with good flow a few days before you bring it home. That way the bacteria bed can be at full efficiency when you transfer it over. Otherwise when you first run it flow might be reduced and some built up sludge may get into your tank.

Agreed with the above, I just wanted to mention that I actually prefer starting tanks with established filters, makes it way easier and takes a load off the mind when you don't have to worry about cycling.

Suckermouth wrote:Agreed with the above, I just wanted to mention that I actually prefer starting tanks with established filters, makes it way easier and takes a load off the mind when you don't have to worry about cycling.

Same here. I usually don't use a whole filter, but just some media from the other filter, or just squeeze the old foam pads into the new filter. Way eaiser than starting from scratch.

Sounds like it isn't too bad an idea then!
I'd definitely give it a quick clean in case there's any sludge in there, and I'm going to get some new water treated within the next few days so it's ready for the new filter and fish when I transfer them in two weeks. Should I give the cartridges a gentle wash too, or leave them be for a while once they're transferred? Lastly, is it worth adding any bacterial supplement to the tank, or is it unnecessary because there's a whole filter being transferred?

Thanks a lot guys! Much appreciated!

You can swish the cartridges around in a bucket of tank water (after a water change) to knock off any loose stuff and you'll be all ready to go. I wouldn't bother with any supplements since you're already starting with a whole seeded filter.

Alright, I'll give that a try then. Thanks again!

Well, it's been running since shortly after the original post, and so far so good!

A quick hello to suckermouth and 2wheelsx2, a couple of fish friends I've sold plecos to a few years ago.

I've used pre-established filters for at least 50 years, whenever possible, to get a new tank up and running asap. Many fish room owners will maintain spare sponge filters in established tanks or a wet/dry filter sump for just such occasions. It's a time tested, good way to avoid starting from scratch.
The alternative of using some established media swished in water to be added to a new tank and filter works but it isn't quite as fast. It has been suggested by some in aquaculture that adding a water conditioner containing "artificial slime" may aid in the attachment of the bacteria to the substrate of new filter media.