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Re: BG algae and trace elements

On Tue, 16 Oct 2001, Olga Betts wrote:
> I have a continuting nightmare with BG algae. No matter what I do  it 
> returns and covers everything with thick slime. I dug out the test 
> kits and tested and low and behold - even though I have been adding 2 
> cc of PMDD daily the Nitrate and Iron readings are *none*! Is there a 
> shelf life to potassium nitrate and trace element mix? (The test kits 
> are okay - not old).

There is no shelf life that I've ever heard of but there are some things
that can effect their potency.  If a potassium nitrate solution is anoxic
for some reason then denitrifying bacteria can destroy the nitrate, but
that usually requires a lot of organic "fuel" for the bacteria to live off
from and I doubt that it happens very often.  The ferric iron chelate in a
trace mix (at least a mix that uses EDTA or DTPA) breaks down in light,
and it can be destroyed very quickly in direct sunlight.  Other chelated
metals are more stable.  If the trace mix is never exposed to light then
it should last a long time.  If the chelated iron has been broken down by
light then a red or ochre-colored sediment may form on the bottom of the

It's conceivable that in a PMDD mix with either EDTA or DTPA and nitrate
that exposure to light could result in some photolysis products that are
consumable by bacteria.  The bacterial action could cause anoxic
conditions and lead the bacterial to denitrify the nitrate.  But that is
pure speculation; I've never seen it happen and in fact I've never used

> Also this tank has now been set up about 8 years. At some point do 
> substrates go bad and need shoveling out? Gad, I hope note! It is a
> terralit and gravel substrate.

I have substrates that have been substantially undisturbed for as much as
14 years.  I don't see any reason to believe that they might "go bad" in a
way that would feed BGA.

My oldest tank did develop a severe BGA problem.  I left conditions in
that tank very stable for a long time.  A couple years ago BGA appeared
along the front gravel line and very slowly expanded to cover the tank.  
It took maybe a year and a half to completely take over. I didn't do much
to stop it, partly because the tank housed some old Botias and I was
worried about how their health would respond to changes, and partly
because that tank had become a long-term experiment in low-tech tank care.

I do wonder if keeping an aquarium under pretty much constant conditions
for a long period will eventually lead to a BGA outbreak.  Natural
environmental conditions almost never stay constant.  Perhaps in an
unnaturally stable tank the BGA ultimately gains an upper hand over other
bugs and takes over.

At any rate, the last of my 15 year old Botias died last month, so I
decided to do something about the tank.  I removed all of the rocks and
tiles from the tank and bleached them and cleaned as much of the BGA out
of the tank as I could.  I removed some sickly plants while I cleaned and
thinned some overgrown patches.  After the cleaning I treated the tank
with erythromycin for three successive days, and doubled the dose on the
last day.  I left the filter media in place during the treatment so that
even the filter media was treated.  I increased the lighting at the same

After the antibiotic treatment I rearranged some of the plants in the tank
and transferred some new plants in from other tanks.  I wasn't ready to
add CO2 to the tank, so I'm trying Seachem's Excel as a carbon suppliment.  
I need to throw in some ramshorn snails to keep the leaves clean.

So far it's working pretty well.  The BGA is gone and I hope that the
treatment and the changes in the tank will reset whatever trend it was
that let the BGA gain dominance.

If you used erythromycin in your tank more than once recently and the
BGA returns quicky then your tank may have developed an
erythromycin-resistent strain.  You may need to use something else next
time.  Last time I checked, copper still killed BGA.

Roger Miller