Filter cycle?

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ksmith3631

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Feb 25, 2021
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Hi,
I have a 55 gallon tank that has an established 350 Magnum filter, I added a second canister filter for redundancy. My question is, how do you know when the new filter becomes established seeing as I should not see any spikes in ammonia and nitrites, because of the established filter?
Thanks.
 

dougall

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Mar 29, 2005
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Is there a source of ammonia? Without one there's nothing to cause a spike

With one, it really depends on size and size of the bacterial colony.

With ammonia source...
Test water, if no ammonia or nitrite but nitrate.. you are likely to be good.

Test tomorrow,if nitrate goes up but the other 2 stay 0,you are golden. If the other 2 are anything other then you are not cycles (with the caveat that chloramines from your water treated with prime will be detected as ammonia, so pay more attention to nitrite and nitrate)

Without a source of ammonia, your bacterial colony is slowly dying.
 
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ksmith3631

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Thanks for the response dougall. It is an established tank with fish in it, so I do have an ammonia source through them. The current filter has been handling the tank well with ammonia and nitrites at 0. Nitrates are a little high, but water changes have kept that to a reasonable level. I purchased Seachem Matrix Bio, which I put in the new filter. I heard that is very good at dealing with Nitrate, so I am hoping that is the case.
But seeing as the old filter is doing the job I didn't know how to tell when the new filter could carry the load in case something happens to the older one.
 
Apr 2, 2002
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Adding a filter to an established tank does absolutely nothing to change the amount of bacteria in a tank. That is only accomplished by increasing the ammonia production in the tank. All that adding another filter will do is spread out where the bacteria lives.

Because the bacteria is basically immobile inside the biofilm it uses to attach to hard surfaces, only a small amount of the bacteria are motile. How much depends on the levels of nitrogen present in the water. When it goes down, the bacteria can sense this and more of them become mobile so they can move to a place which has what they need. When they have that where they are, the numbers that are motile will decline.

Because the bacteria are relatively immobile, where they will have the greatest concentration of numbers is where the things they need are regularly available. What they need is basically oxygen, ammonia/nitrite an inorganic carbon (carbonates/bicarbonates.CO2). There are other things they needs as well such in smaller amounts. All of this must be delivered to them inside the biofilm.

So, adding a filter doesn't increase the number of bacteria. What will happen over time is that some of minimal bacteria that is mobile will land in the new filters. They will start to multiply there. At the same time they will slow or cease multiplying elsewhere. So in a matter of weeks what will happen is the total amount of bacteria in the tank will not change, it will, in effect, move to other locations.

The bacteria doesn't do this by actually packing up and moving elsewhere. It happens by where the bacteria multiplies and where it does not.

At the center of the entire cycle is ammonia. The level of ammonia determines both which strains of bacteria will colonize and in what sort of numbers. The more ammonia that gets processed into nitrite, the more nitrite oxidizing bacteria will colonize. Finally, if conditions are right, there will also be denitrifying bacteria colonizing as well. However, these need an anaerobic environment so are harder to have establish in many tanks.

This boils down to a supply and demand type situation. The ammonia is the supply and the bacteria are the demand. When there is excess food, the bacteria multiply. When food is in short supply they do not. This means the size of the bacterial colony in a tank will always size to the available levels of ammonia.

Think of this in terms of a fishless cycle. Set up three tanks of equal size, contents and filtration. In one add ammonia to produce 1 ppm, in another make that 2 ppm and in the third make it 3. You will see two results. First, the tank with 1 ppm will be cycled the soonest and the one at 3 ppm will take the most time to become cycled. This also means there are more bacteria in the tanks cycled using 2 ppm than using 1 and that the tank getting 3 ppm will have the most bacteria and will be able to handle the biggest fish load.

The number of filters on each tank will do nothing to change how much bacteria colonizes in each tank, the amount of ammonia available is the determining factor.
 
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FreshyFresh

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Thanks for the response dougall. It is an established tank with fish in it, so I do have an ammonia source through them. The current filter has been handling the tank well with ammonia and nitrites at 0. Nitrates are a little high, but water changes have kept that to a reasonable level. I purchased Seachem Matrix Bio, which I put in the new filter. I heard that is very good at dealing with Nitrate, so I am hoping that is the case.
But seeing as the old filter is doing the job I didn't know how to tell when the new filter could carry the load in case something happens to the older one.
I wouldn't rely on seachem matrix to remove nitrate. One of the reasons we do water changes on our tanks is to reduce the nitrate level. How often are you doing water changes and how much water are you changing? I never do less than a 50% water change.

It is wise to run two filters on tanks for redundancy. If one has issues, the other will still offer filtration. In regards to your original question, could you take the new canister off the established tank now and setup a new tank with it? You can, but i wouldn't try it until the new filter ran on the old tank for maybe 6 weeks or so. Still no guarantees for all the reasons TTA mentioned above.
 
Apr 2, 2002
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Well it is not that simple.

When the ammonia (or other essential nutrients) disappears, the bacteria sense this and they do go dormant. That is not the same thing as the levels dropping in half for example.

There are two things to focus on here. One is the bacterial colony which keeps our tanks safe and then the individuals that make up that colony. The bacteria in a fully cycled tank with everything they need are like the population of a country. Every day individuals die and every day individuals are born. The population as a whole may remain stable while the individuals making up that population are always changing.

When the bacteria go dormant, they stop reproducing. However, they are not dead. Every day the colony is dormant some individuals will die and none will reproduce. However, the death rate is much lower than it would be if the colony was awake and functioning. Over time enough individuals will die such that the ammonia/nitrite oxidizing capacity of the colony will decline. Now when the ammonia comes back and they revivie, there are no longer enough individuals remaining to process as much ammonia as the colony could when it went dormant.

However, for a very long time some individuals will survive. All it takes to start a colony is one single bacterium. However, the amount of time it would take for one cell to result in a viable colony would be quite long. However, for the survival of the "species" all it takes is one individual able to reproduce. Which is why these bacteria have survived for millions of years.

On the other hand, if all of the ammonia is not gone, the bacteria will stop reproducing until the size of the colony shrinks to the point where it can survive on the available level of ammonia. Should more ammonia than they need to thrive become available in the future, they will multiply in response to this. There is no dormancy going on in this situation.

Suppose you have a fully stocked tank and for some odd reason you needed to remove say 75% of the fish for a month. Further, you wanted to be able to return the fish to the tank and have it still be fully cycled. You have two choices. Remove all of the fish and return them all in a month or remove the 75% and leave the other 25% in the tank. At the end of the month you would yhen return the other 75%.

If you move out 100% of the fish, the ammonia goes away and the bacteria go dormant. In a month, when you return the fish which start making ammonia, the bacteria wake up and very soon are handling all of the ammonia. Not enough individuals will have died to matter. On the other hand, remove 75% of the fish load and leave the rest behind, and the bacteria will have stopped reproducing. Many individuals will die and the colony size will shrink. When you return the 75% you will experience some unwanted cycling issues. You may even lose fish.

As always, having live plants in a tank will change things. How much depends on how many and what sort of plants are involved.
 
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