How Long Till A Sponge Filter Has Bacteria?

[Saltinthedesert]

Getting a new 20g tank tomorrow. Dropped a brand new sponge filter in my well established and cycled 75g this evening.
 

1. How long does the sponge filter need to be running on the air pump in my old tank before it’s going to be useful when I transfer it to “cycle” my new tank for me?

I’ll be filling half of the 20 with water (I know this doesn’t hold much good bacteria) from my 75 and moving a few plants over too. 
 

2. Does a separate sponge from my old canister filter that’s been sitting on the bottom of my 75 (not attached to air) also have good bacteria in it? It’s been in for weeks. 

[AnimalNerd98]

1) I would say about 2-3 weeks at minimum, a month is where I would feel more comfortable in saying it is well "seeded." 

2) By bottom, do you mean the bottom of the canister filter or bottom of the aquarium itself? Either way, I would take that sponge and wring it inside the 20 gallon with some dechlorinated water. Get it all mucky and cloudy, that will seed it very nicely. Bring over some of the substrate from the 75 gallon, that would help jump start it as well. 

An aside: when I set up new tanks, I just throw in an extra sponge filter from my established 20 gallon planted tank. I will toss in a handful of gravel from the 20, and a bunch of plants (especially fast growing or floating plants) to suck up nitrogenous waste. I stock lightly with snails or shrimp first, get some poop going, watch for plant/algae growth, and then add fish. 

Edited June 6, 2021 by AnimalNerd98

[Guppysnail]

I do all my new tanks exactly the way @AnimalNerd98 described and never have a problem. The fast growing stem plants are the key. 

[gardenman]

There's useful and there's useful. Bacteria in an established tank is largely omnipresent. Within seconds of the new filter hitting the tank some bacteria would be in it. Would it be enough to be meaningful in a new tank? No. I think two to three weeks of use in an established tank would make it much more efficient when moved, but even an hour is better than nothing. In just an hour it would have picked up some, maybe quite a lot of bacteria and be more useful than a sterile sponge filter right out of the box.

[BenA]

Had to remove a fish in a rush as it was attacked and injured. I had no spare filter so had to create one fast. I bought an air sponge filter and dumped it into a bucket full of mucky water from another tank that was cleaned earlier, on top, I also attached with elastic bands a small sponge that I keep on the bottom at another tank, had no issues and water parameters are good. The fish survived recovered and back to normal behavior so I am happy.

Edited June 6, 2021 by BenA

[lefty o]

a few days to a week in an established tank. caveat being, when you drop it in the new tank, the ammonia and chlorine in that tank cant be so high as to kill off the good bacteria your sponge now has in it.

[HH Morant]

This is a very interesting question, something I have wondered about. I think the anecdotal evidence described in the responses is helpful and the experiences described are cumulatively probative. Does anyone know of any scientific evidence on this issue?

[lefty o]

i cant quote anything, but there has been testing etc on bacteria growth in an aquarium.  once you have bacteria started, it is something on the order of it doubles every couple of hours. this also assumes that the bacteria finds enough food in the aquarium for it to keep consuming promoting its growth.

[gardenman]

I have a suspicion that a lot of the gunk in a sponge filter that we wash out when we clean it is in fact, the good bacteria. I've watched stuff floating around in a tank with a sponge filter and I've yet to see anything get pulled into the sponge filter. If something happens to land on the filter it tends to stay there, but I've seen very small stuff (flake food for example) drift right down alongside of the sponge filter and never move towards it. Maybe it's the flow rate on my filters, but as mechanical filters, they're not especially effective. I don't know if anyone has done an analysis of what comes out when you clean a sponge filter, but my suspicion is that much of the gunk we wash away is bacterial growth. Which brings up the interesting question of "Should we clean our sponge filters?" Washing away the bacteria we need seems counterproductive. Is a filthy, dirty, sponge filter better than a freshly washed one? Do we hurt our tanks by washing our sponge filters? I don't know. 

[HH Morant]

Gardenman, I think you make a good point. Bacteria grows on surfaces, so a lot of the bacteria is probably growing on the surfaces of the particles of gunk in the filter. When you clean the filter these particles go down the drain and you lose the bacteria growing on them. But if bacteria is growing on the gunk particles, it is also on the sponge filter itself, so you retain that bacteria, which multiplies and grows on the new gunk the filter collects out of the water column. This cycle is probably healthier than not cleaning the filter because leaving the gunk in your aquarium indefinitely is going to create ammonia as it decomposes.

[HH Morant]

And if the filter is not effective at pulling particles in from the water column, where is the gunk coming from?

[HH Morant]

Now that we have thought this through, if you are moving a seasoned filter to a new tank, it makes sense not to clean it so that you get the benefit of the bacteria on the surfaces o the gunk particles.

[BenA]

21 hours ago, HH Morant said:

This is a very interesting question, something I have wondered about. I think the anecdotal evidence described in the responses is helpful and the experiences described are cumulatively probative. Does anyone know of any scientific evidence on this issue?

from Aquariumscience.org:

4, Over Cleaning the Filter

If you are cleaning your biofilter media more than once every four months to a year,  you need to stop. The brown gunk in the filter is good beneficial bacteria and shouldn’t be cleaned until it plugs up. Actual testing of a sponge filter confirmed that a thorough cleaning is a very bad thing to do to a filter. Click on the following link for some interesting test data:

6.8. Thorough Cleaning (aquariumscience.org) 

[HH Morant]

15 minutes ago, BenA said:

from Aquariumscience.org:

4, Over Cleaning the Filter

If you are cleaning your biofilter media more than once every four months to a year,  you need to stop. The brown gunk in the filter is good beneficial bacteria and shouldn’t be cleaned until it plugs up. Actual testing of a sponge filter confirmed that a thorough cleaning is a very bad thing to do to a filter. Click on the following link for some interesting test data:

6.8. Thorough Cleaning (aquariumscience.org) 

BenA, that is a great article. I did not know about that website. I am changing my schedule for cleaning my sponge filter, my canisters, and my canister pre-filters. When I do clean them, I will clean one at a time, and try not to get them "too clean."

[BenA]

HH Morant

I came across the site due to a post in this forum and learnt lots from it. I don't follow everything he says but at least it is due to understanding rather than parroting. It is a very good site indeed. 

Edited June 7, 2021 by BenA

[Saltinthedesert]

Thanks everyone for the thoughtful replies. Here is a pic from the 20 long in question. A bit murky because anytime you touch the Fluval stratum is kicks up all that “water dust”. 

[Fish Folk]

 Bacteria colonize all over an established aquarium. As a result, like others have said, I move out well-established sponges _from there_ over to new tanks, and put new sponges in the well-cycled, established tank. This makes it quick to set up a new tank.

For your question, I think 2x weeks _in a cycled tank _ for a bacteria colony to be started  on a new sponge is a safe guess. But 3-4 weeks for a full colony to process the specified Aquarium volume per sponge size is a safe estimate. So, after 2 weeks, I think you could get away with adding one hardy fish safely. But after a month, you should be safe to fully stock.