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Science Project

> From: sierrahotel <sierrahotel at flex_net>
> Subject: Science Project
> My son is considering a science fair project using a DIY CO2 to compare
> plant growth in parallel tanks with and without CO2.  Any suggestions as
> to what sort of plant, substrate, fertilization etc. should be used
> would be appreciated.   We are thinking elegans (elodea)
> We have 7.2 Ph, hard well water.  Plan to buy couple of cheap 5 gals and
> hang shop light across them, measure plant growth in millimeters/day.

Anacharis (elodea) is good because it requires no substrate, but as
mentioned before, it can break down carbonates in the water on its own. 
It would probably be the easiest to work with though, because it is
fully aquatic and will not produce emersed growth.  

Hygrophila spp. might be better, but they are capable of producing
emersed growth.  Emersed growth gives the plants access to atmospheric
CO2, allowing them to effectively cheat.  It may be a toss-up though,
since Anacharis can remove carbonates from the water.  H. polysperma is
less likely to produce emersed growth than H. difformis, but is also
more fragile and susceptible to nutrient deficiencies.

I would recommend starting with bare tanks and bleached plants.  The
bleach will set the plants back a bit, but will eliminate many potential
skewing factors like filamentous algae or hungry snails.  If you don't
want to use bleach, you can use Hydrogen peroxide instead.  An APD
archive a few months back gives the appropriate concentration of
peroxide to equate to a 5% bleach mixture.  I think you just use
straight 3% peroxide, but I don't want you to kill your starter plants
on my bad advice.

As mentioned before, weigh the plants in addition to measuring them. 
Beware that the plants will branch, and measuring may become more
difficult at that point.

For fertilizer... Hmmmmm....  I haven't been successful with Miracle
Gro, but you might try it or something else that someone on this list
suggests.  Mix it up like you would for your house plants and then feed
a teaspoon or so to the plants.  Monitor and chart pH, hardness,
ammonia, and nitrate levels in the water.

David W. Webb
Live-Foods list administrator