[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: sugar eliminates nitrates

> Date: 19 Apr 97 12:58:27 WAT
> From: Rodney Dorville/EC/SP_SF <RDORVILL at sp_ac.sg>
> Subject: Re: Sugar eliminates nitrates
> >     As one netter explained, "the sugar is used as a carbon source by 
> >     denitrifying bacteria and speeds their ability to reduce nitrates." 
> >     The recommended dosage is about 1 teaspoon per 50gal.
> Run this by me again...
> I thought that denitrifying bacteria converts nitrites to nitrates.
> Nitrates are only removed using
>  a.  plants
>  b.  regular water changes
>  c.  some anaerobic bateria which converts them back to ammonia.
> Rodney

I'll respond here, not because I had anything to do with the original 
post, but because I think its interesting, and I have a big mouth :).

The anaerobic bacteria in c, above are the "denitrifying bacteria".  They
reduce nitrate to nitrogen gas.  The bacteria you refer to as converting
nitrites to nitrates are "nitrifying" bacteria, or more specifically
"nitratifying" bacteria. 

The denitrifying bacteria do need reactive organic compounds to fuel
denitrification.  Sucrose would be reactive.  They also need at least
marginally anaerobic conditions.  After some calculations, it looks to me
like the recommended dosage of 1 teaspoon per 50 gallons would work out to
roughly 9 mg/l of dissolved organic carbon, which is in line with (perhaps
a little higher than) what many of us might have in our public water

If you're a reefer, using RO water to make sea water and/or stripping
organics out of the water with a foam fractionater, then you might need 
to add sugar to have very much organic carbon in solution at all.  
Without it, you probably won't see much denitrification.

I haven't measured organic carbon levels in lots of aquariums (hmm... or
any aquariums, come to think of it) but I suspect that planted tanks
normally have a substantial levels of dissolved organics in them - perhaps
in excess of the amount the reefers are adding.  I don't know whether
these would be reactive molecules or not.  I've read in technical
literature that aquatic plants (which often means algae) "leak" some of
their fixed carbon, so the simple fact of having plants in a tank might
mean that you already have a constant supply of dissolved organics which
might fuel denitrification.  No additional sugar needed.  Maybe some of
the plant scientists on the list could comment on that. 

I can't say anything at all about whether denitrification is going to help
control algae.  However, I'd have to be shown that denitrification would
be accelerated by adding sugar to a planted tank.  Instead, I think you'd
just be feeding the heterotrophic aerobes in your filter.  They'll love
ya' for it. 

Roger Miller