Re: Antibiotics for cyanobacteria

>From: "Olive K. Charlsey" <achaudh at emory_edu>
>Date: Thu, 13 Jun 1996 16:33:53 -0400 (EDT)
>Subject: Antibiotics for cyanobacteria
>	I recently treated my tank with 2.5mg/l of erythromycin to get 
>rid of some cyanobacteria that were beginning to grow over my lileopsis. 
>The treatment worked for a majority of the bacteria, but there are still 
>a couple of small patches left after 4 days. Are there any other 
>antibiotics that can be used against Gram negative bacteria that 
>will not damage the plants or cause any other excessive harm? 

I once used Kanamycin when I could't find erythromycin. This is another
'mycin' sold in aquarium shops. It worked fine. I think others have also
used it on 'resistant strains of blue green algae (another name for
cynaobacteria). Regarding your use of erythromycin, you might want to wait a
few more days before you give up on its effectiveness. I have found that its
and other algicide's effects are not noticed immediately. You did not say
how many daily treatments of erythromycin you used.  The label for fish
disease recommends 1 200mg capsule per 10 gallon(40 liters), for several
days. This corresponds to 5.0 mg/l per day. As you also did, I usually try
1/2 dose or 2.5 mg/l. I have found this to be effective and notice that the
BG starts to decline within a week. After I gather up the blob of dead algae
together with other bottom debris and a little syphoning, it is (atleast
temporarily) gone! <g>  Yes folks, I TOO get BG algae. And it may
periodically come back. And my fish occasionally get ich (when I forget to
crank up the heaters in the late fall). These events seem to be the normal
course of nature. :-)

You might want to stay with the erythromycin before you go to another
antibiotic. We do not want you to be developing any super resistant strains
of BG bacteria.<RBG> You have several degrees of freedom left with the
erythromycin; if you haven't already done this.... you could double the
daily dose and/or increase the duration of treatment (up to label
recommendations). THis will give the erythro more capability to fully zap
any resistant cells. That's why the MD's tell their patients to treat an
infection for days (weeks) longer than the symptoms are present. 
If it were me, I would leave the filter going to kill the BG which may be in
the filter, but be prepared for a big die off of your nitrobacteria (both in
the filter and elsewhere). To be conservative, feed sparingly or nothing
during the treatment to reduce the chance of an ammonia/nitrite peak.
However, if you have lots of plants, you might not measure any ammonia in
either case. I have always found the plants to perk up after the antibiotic
treatments, either due the increase in light (once the bg is removed from
their leaves) or from the ammonia snack! I WOULD LOVE FOR SOMEONE WITH AN

N. Frank

Neil Frank, TAG editor    Aquatic Gardeners Association    Raleigh, NC USA