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Soil Substrate and Green Water

Karen recently commented about the prevelance of green water outbreaks in
the tanks of those who use soil substrates, possibly due to phosphate
leaching. In the same issue, Christopher Coleman commented about the
presence of algae at the glass/substrate interface in his tank on occassion.

I'm definately not in any camp - I don't use bleach, I can't seem to find
real SAE's, and I use a variety of substrate/fertilizer combinations in my
various tanks. Algae does NOT send me thru the roof, so long as it isn't
overgrowing my plants or obscuring the water column of the tank. A bit of
green algae on the front glass is easily removed during my weekly
maintenance, I don't really sweat it.

But I have noticed something in _my_ tanks which might be related. I live in
Toronto, which gets it's water from Lake Ontario, an inland "sea" surrounded
by heavy industry and lots of agricultural land. Since I moved to Ontario
back in the early 80's, whenever I set up an aquarium using tap water I get
green water and furry plants if I use lots of light. I have noticed this on
tanks placed outdoors on my north facing balcony in the summer (so green you
can't even tell if there are any fish in them) and in tanks inside under
varying amounts of fluorescent or metal halide light. I have spoken to other
aquarists in Toronto who use tap water with no problem. Perhaps Lake Ontario
water has high phosphate levels from agricultural runoff or perhaps the
water picks up something on its way from the treatment plant to my faucet -
I know that the piping in my building is still largely cast iron. But
whatever the source, something in _my_ tap water is beloved of algae.

To solve the problem, several years ago I bought a TFC Reverse Osmosis
filter. I currently have a number of tanks running which use R/O water
exclusively. One is a soil based tank, another has Flourite as a substrate,
and a third uses AquaTerra under gravel. I use different fertilizers/iron
supplements in these various tanks and notice that if I get overly generous
with the "daily drops", I will see an increase in green algae on the front
glass (again, easily removed during my weekly maintenance, when I do my
regular 25% water changes. But in NONE of these tanks do I see any _problem_
algae. No algae blooms, no overgrowth of fine leaved plants. Certainly there
IS some algae (remember I don't get upset over a little bit of the green
stuff). I also frequently see algae at the glass/substrate interface (again,
very easy to remove).

Now, a few weeks before Christmas I bought quite a few new plants and as I
wasn't ready to set up complete tanks for them at the time, I potted them
individually in clay pots with a combination substrate of
gravel/soil/gravel, and placed these pots in three separate spare tanks. One
got filled with the same R/O water which I use for my other tanks and the
other two got plain tap water because my R/O water filter could not produce
pure water fast enough for my needs at that particular time. I notice now
that the one which was filled with R/O water has only minor algae present,
mainly on the front glass. The other two, which were filled using water
straight from the tap, are so pea soup green I can't even see anything other
than "suggestions" of plants inside. I don't bleach my hands/arms/nets as I
work from tank to tank so it is quite possible for me to transfer algae
spores from one tank to another during maintenance. But I still don't see
problems in those tanks which use R/O water, even the one which uses Steve's
HTBASS methodology. So, just because there are algae spores present, you
won't necessarily get a _problem_ tank, provided that the water in the tank
is not conducive to explosive growth of those spores.

So while "leaching" of nutrients out of a substrate might play a part in
algae problems, at least in _my_ tanks, the source water seems to me to be
of far more concern. Also, just because your local water utility might
certify the contents of what it produces, that is at the source, not as the
water comes out of your faucet. Maybe I have a gremlin sitting in the
basement of the building, quiety injecting phosphates into the water
destined for my kitchen faucet <g>.

James Purchase
Toronto, Ontario