# Does FURAN-2 kill beneficial bacterial in the filter?



## Merriallynchian (Apr 25, 2017)

Does API FURAN-2 medicine kill beneficial bacterial in the filter? 

Thanks.


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## Discusluv (Dec 24, 2017)

No, it does not. Your beneficial bacteria is gram positive and Furan 2 only kills gram negative bacteria.


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## Darkblade48 (Jan 4, 2008)

Discusluv said:


> No, it does not. Your beneficial bacteria is gram positive and Furan 2 only kills gram negative bacteria.


Which beneficial bacteria are Gram positive? 

_Nitrosomonas _and _Nitrobacter _are both Gram negative.


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## Discusluv (Dec 24, 2017)

I am sorry, I have been for many years wrong then.
I have used this antibiotic with very sensitive fish ( discus, primarily) many times throughout the years with no noticeable effect to my bio-filter. I do have well established systems, however.
I am not saying you are wrong, because you are right, I liked it up and both Nitrosomonas and Nitrobacter are stated as gram negative.
This is mystifying to me.

This could be part of the problem:
On API's website it clearly states that Furan 2 does not damage the bio-filter. 
When the company itself states this, there is bound to be some confusion. 
Still not doubting the point you are making, let me be clear. 
https://www.apifishcare.com/product.php?p=details&id=634#.W1EwlLgnZPA

When my fish are sick, however, I change water daily regardless of ailment or medication using. 
This could explain why a decrease in nitrifying bacteria is not evident to me.
I do appreciate you bringing this to my attention. This could very well make a difference on newly established bio-filters and I will now caution others that this could set-back ones bio-filter.


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## Merriallynchian (Apr 25, 2017)

Discusluv said:


> I am sorry, I have been for many years wrong then.
> I have used this antibiotic with very sensitive fish ( discus, primarily) many times throughout the years with no noticeable effect to my bio-filter. I do have well established systems, however.
> I am not saying you are wrong, because you are right, I liked it up and both Nitrosomonas and Nitrobacter are stated as gram negative.
> This is mystifying to me.
> ...


Does your tap water use Chlorine or Chloramines? If Chlorine, then using the water conditioner will neutralize the Chlorine however if your tap water is chloramines then you are left with a high ammonia byproduct even with heavy water changes. That is the problem I'm facing now is I am trying to do water changes and ended up with ammonia spikes which my biological filtration is unable to handle. 

If the beneficial bacteria are gram negative, I wonder why the medicine does not kill it along with the bad bacteria? Maybe the beneficial bacteria are more resistant to the medication ? 

Thanks.


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## Mike A. (Jan 6, 2018)

Just to further confuse you, I think that the "2" in Furan-2 is intended to reflect that it's effective against both gram-positive and -negative bacteria.

But it's more complicated than simply whether gram-positive or -negative. Bacteria exist in lots of various forms and with structural differences in outer surface protein layers, etc. So it may be that antibiotics like Furan-2 just aren't as readily absorbed either into the individual cells themselves or can't get through multiple layers of bacteria built up over time or other things like that given the dosage and time present. I've not really studied it, but I'd guess that it very likely may have some effect on various beneficial bacteria but there's enough that's not affected that for practical purposes it's safe. Given higher concentrations/time/temp/newly established tank, etc., that might not be the case.


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## Darkblade48 (Jan 4, 2008)

Mike A. said:


> Just to further confuse you, I think that the "2" in Furan-2 is intended to reflect that it's effective against both gram-positive and -negative bacteria.
> 
> But it's more complicated than simply whether gram-positive or -negative. Bacteria exist in lots of various forms and with structural differences in outer surface protein layers, etc. So it may be that antibiotics like Furan-2 just aren't as readily absorbed either into the individual cells themselves or can't get through multiple layers of bacteria built up over time or other things like that given the dosage and time present. I've not really studied it, but I'd guess that it very likely may have some effect on various beneficial bacteria but there's enough that's not affected that for practical purposes it's safe. Given higher concentrations/time/temp/newly established tank, etc., that might not be the case.


To add even more confusion, the beneficial bacteria that we have that reside in the filter (on filter media) likely exist in biofilms. These are naturally resistant against antibiotics, and antibiotics really only work effectively on planktonic cells.

It's hard to say exactly what effect drugs in general will have on microbial communities that exist in biofilms; it is still a very active area of research


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