Losing Biofilter after Fish Loss?

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tackful

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Mar 15, 2007
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Hi Again,
A few weeks ago many of you were kind enough to help me with a large fish die-off problem, since solved (Thread: Unexplained Fish Loss). Before then, my tank had happily supported 14 tetras for years, but for over two weeks now it's been down to just three. Restocking might not happen for a while as the rummynose tetras I am so fone of are hard to find.
In the meantime, is there something I can do to maintain my biofilter at it's previous 14-fish capacity despite having only three fish in the tank? Thanks.
 

FreshyFresh

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Jan 11, 2013
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I don't think there's anything you can do while the remaining fish are in the tank, if you value those fish.

The existing BB colony will adjust relatively quickly one you go from 3 back to 14. I would monitor water params for the first week and feed lightly.
 

FishAddict74

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I don't think there's anything you can do while the remaining fish are in the tank, if you value those fish.

The existing BB colony will adjust relatively quickly one you go from 3 back to 14. I would monitor water params for the first week and feed lightly.
+1
 

Wyomingite

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Oct 16, 2008
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I don't think there's anything you can do while the remaining fish are in the tank, if you value those fish.

The existing BB colony will adjust relatively quickly one you go from 3 back to 14. I would monitor water params for the first week and feed lightly.
+1. Also you should only add 5 or 6 fish at a time, as long as you keep tetras. Some people may say 3 or 4. Regardless, adding fewer fish ensures you don't have a large ammonia spike due to the fact the bacteria can't reproduce fast enough to handle the ammonia created by the new fish. If you were adding larger fish, that number would be fewer.

WYite
 

fishorama

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Jun 28, 2006
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Beneficial bacteria kind of goes dormant & can double in 24 hours or less. That's why you need to test & use Prime (or similar)...to keep the ammonia in a safer form (ammonium) until BB catches up. To be really safe you can add only a few fish at a time like Freshy & Wyite said...or add more, test more & & add Prime more (every 24-48 hours). If you have many live plants that may be less, plants like ammonia! But they need to be fairly fast growers to help much...Test often!
 
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Apr 2, 2002
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There is a difference bewteen the viability of a bacterial colony and an individual bacteria. In tanks we have a working colony. While the relative number of bacteria present may remain fairly constant, individuals are naturally dying and others are reproducing to replace them. So even while the individuals are changing, the colony, as a whole, does not.

The bacteria will only go dormant when there is no ammonia. Otherwise the colony sizes up or down accordingly.

The bacteria reproduce by dividing. The division is triggered by the presence of more ammonia or nitite than they can use. So they divide. However, if the amount of ammonia in a tanks is reduced, they do not divide. The natural deaths are not repalced by new dicisions and the size of the colony shrinks.

When the bacteria go dormant because their prime nutrients (nitrogen and oxygen) are gone, they will stay that way until what then nedd is back. Over time there will be a loss of individuals. After enough loss the colony, when revived, will not have the same capacity. In terms of a tank and cycling. if they are dormant long enough, when they wake there will be no difference between what happens then or if one were starting a new cycle from scratch. There are enough survivors to seed a new colony but not nearly enough the be one they were when they went dormant. All it takes to establish a new colony is a single individual. This is why the nitrifying bacteria have survived for so long without forming spores. Ain't nature grand?

What this means here is that you have a short window to begin adding more fish before the number you can add gets smaller. Ultimately, you are basically back into a fish in cycle and must restock gradually.
 
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BrianP55

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Feb 16, 2021
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Hi Again,
A few weeks ago many of you were kind enough to help me with a large fish die-off problem, since solved (Thread: Unexplained Fish Loss). Before then, my tank had happily supported 14 tetras for years, but for over two weeks now it's been down to just three. Restocking might not happen for a while as the rummynose tetras I am so fone of are hard to find.
In the meantime, is there something I can do to maintain my biofilter at it's previous 14-fish capacity despite having only three fish in the tank? Thanks.
I suspect that your bacteria are just fine. However, if you feel the need to feed them, you will need to provide them with an alternate carbon source, just as you would do if you were cycling a new tank. I use organic cane sugar for cycling.
 
Apr 2, 2002
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The autotrophic nitrifying bacteria only use inorganic carbon, usually from carbonates/bicarbonates of CO2. Their prime energy source is ammonia or nitrite. Sugar will do nothing to maintain a cycle. For that you need ammonia. In fact, glucose and organic carbon inhibit nitrification:

Strauss, Eric A., Lamberti, Gary A., (2000), Regulation of nitrification in aquatic sediments by organic carbon, Limnology and Oceanography, 8, doi: 10.4319/lo.2000.45.8.1854.

Abstract

Nitrification, the microbial conversion of ammonium to nitrate, is an important transformation in the aquatic nitrogen cycle, but the factors regulating nitrification rates in freshwater ecosystems are poorly understood. We investigated the effects of organic carbon quantity and quality on nitrification rates in stream sediments. First, we hypothesized that when environmental C: N ratios are high, heterotrophic bacteria are subject to N limitation and will outcompete nitrifying bacteria for available NH4+, thereby reducing nitrification rates. In laboratory experiments, organic carbon amendments (30 mg C L−1, as glucose) to stream sediments completely inhibited nitrification with or without addition of NH4+ (P < 0.0001), whereas amendment with NH4+ only (0.75 mg N L−1) increased nitrification by 40% compared with unamended controls (P < 0.0001). Carbon amendments also increased microbial respiration rates over controls by 4–6 times. Therefore, organic carbon additions significantly decreased nitrification rates but increased total microbial activity. Second, we hypothesized that carbon of high quality would have a stronger negative effect on nitrification than would carbon of low quality. To stream sediments, we added organic carbon as either glucose (higher quality) or sugar maple leaf extract (lower quality). Nitrification rates were reduced by the addition of either organic carbon source but were more severely inhibited by glucose (P = 0.001). Our results suggest that organic carbon is an important regulator of nitrification rates and is of key importance in understanding N dynamics in freshwater ecosystems.
from https://aslopubs.onlinelibrary.wiley.com/doi/pdfdirect/10.4319/lo.2000.45.8.1854


Under no circumstances should one add sugar to a fresh water tank it will inhibit the autrophic nitrifiers. it will however cause the reproduction of heterotrophic bacteria which are not wanted. I only post the above study, but I can provide more if people need to see them.
 
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