More aquarium biology for kids

[JoAnn Amber <elmtreeacademy at yahoo_com>]

Thanks everybody, for your help and encouragement,
both in the digest and in off-line communications.

There doesn’t seem to be much aquarium-based middle-
and high school level science material, yet.  It looks
like I’ll have to build a lot of it from scratch, but
at least I’ll have some assistance. <smile>  I’ve had
some good suggestions for studies of aqueous chemistry
and plant nutrition and am looking for (or building)
some activities based on those suggestions already.  I
hope to find ways to adapt activities/experiments
designed for terrestrial plants for use with aquatic
plants. I have some fairly reasonable activities
planned for animals, but still have a lot to do for
the ecosystem as a whole.  I’m always open to
suggestions!   *grin*

Perhaps some of you can help me with this:
I found an experiment in an old biology book that
addresses nutrient deficiencies in plants.  It uses
terrestrial plants growing in a nutrient solution, but
it should apply equally well to aquatic plants and
actually be easier to set up.  It suggests 6 different
nutrient solutions:
(The following combinations each dissolved in 2L of
distilled water – I would use R/O)
1. Normal:  1g  potassium nitrate, 0.5 g magnesium
sulphate, 0.5g  ferric phosphate, 0.5g calcium
sulphate
2. No nitrogen:  substitute 1g potassium sulphate for
potassium nitrate, others unchanged from Normal
solution
3. No  phosphorus: substitute ferric sulphate for
ferric phosphate, others unchanged
4. No iron: substitute sodium phosphate for ferric
phosphate, others unchanged
5. No magnesium: omit magnesium sulphate
6. No calcium:  omit calcium sulphate 

A seventh plant would be grown in unsupplemented
distilled water.  The book suggests that the nutrient
solution be bubbled daily to “maintain a supply of
oxygen to the roots”.  Plants grown in the various
solutions would be monitored (over the course of a
month or so) for growth (height/length) and general
health (yellowing, deformity, dropping leaves).

My questions are as follows:
1. The containers recommended by  the book are mostly
closed – only two holes in the cap.  Bubbling isn’t
going to help much if there isn’t a good supply of air
above the nutrient solution, is it?  Wouldn’t it make
more sense to leave the solution open to the air and
bubble them all continuously?  Or is there an even
better way?
2. What would make a good substitute for the potassium
nitrate so we could make a no potassium solution as
well?
3. Are the solutions given above practical, or are
there better ways to mix them?
4. I’m thinking of using egeria densa because it’s
easy to maintain and a fast grower.  
Does anyone have a better suggestion?
5. Wouldn’t we develop algae problems that might
affect the study?  The book suggests keeping the
nutrient solutions covered and dark, but that’s not
feasible if I want to use aquatic plants.  Any
thoughts?
6. Can anyone think of ways to improve this
experiment?


If you feel that this subject is too far off-topic or
otherwise inappropriate to this list, please let me
know and I'll stop.  Feel free to e-mail me privately
about it if that makes you more comfortable.

My continued thanks for all your help.



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