Ecology experiment - suggestions ?

in article , Limnophile at
wrote on 5/25/04 8:14 AM:

I'm going to try the ecosphere idea again, and I'd like some suggestions, or
corrections if anything written here is a bad idea.

I plan to use an old gallon jar ( 3.8 liters) with a tight-fitting lid, a
cup of pond mud, a cup of used aquarium gravel, about a dozen leaves of
duckweed ( Lemna minor) , a small Hygrophila plant, a small Anacharis plant
, some small bits of algae, some copepods, 3 small snails, and 3 ghost
shrimp. I plan to leave about 1/2 a liter of air in the top when I seal the
jar. The room temperature is a constant 72 to 77 F , and the jar will be
placed next to a west-facing window.

Any species I should add or leave out ?
Anything here sound like a problem ?
Any other ideas ?

Limnophile


I worry a bit about the duckweed. In ponds it usually signals a not very
healthy pond ecology. It cuts off light to plants beneath it, I tend to
think it cuts down on the surface area of the water, limiting the exchange
between water and air. Of course the hope is that the plants will free
sufficient O2 to take care of the animals' needs, and the light will come
from the side, not down through the duckweed. Still, if it were me, I'd
skip the duckweed.

That and, I used to take customer service calls regarding a commercially
available ecosphere, and what I learned there was that you want a very light
animal population, compared to the plants.

I also worry a tiny bit about the pond mud. If there is stuff in the mud
that is decaying (and there does tend to be), the decay process will use up
O2, too much decay could suffocate the animals. But I really like the "live
cultures" aspect. So I'm torn. Go lightly on the pond mud.

Please let us know how everything goes.

-Chris


--
Chris

I decided to use a 5 gallon plastic bottle instead of a gallon glass one, to
give more space and margin for error.

The idea of including the mud is to make sure there are enough bacteria and
other decomposers. I will only use a small amount of mud, and leave the jar
open to the air for about a week so anything organic finishes decaying
before I seal it.

As you said, duckweed might be a bad idea. On the other hand, how do I know
for sure until I try it out ? I will only put in a few leaves to start with.
If it causes a big problem, I can dump out the jar and try again...

I'll also include a lot of algae and plants compared to the amount of
animals. I was thinking of putting 5 glass shrimp, 5 small snails, and 1/4
pound of plants and algae in the 3 gallons or so of water. That should be
something like 120 grams of plants to less than 5 grams of animals. 2
gallons will be used by the mud, gravel, and a large air space at the top.

I was also thinking of including 2 grams of marine salt mix, to provide
iodine and other trace elements. The plants and animals should easily be
able to tolerate 1/6 part per thousand of salt, right ?

Thanks for the suggestions. Any other ideas ?

Limnophile

"Chris Oinonen Ehren" wrote in message
...
in article ,
snip
I worry a bit about the duckweed. In ponds it usually signals a not very
healthy pond ecology. It cuts off light to plants beneath it, I tend to
think it cuts down on the surface area of the water, limiting the exchange
between water and air. Of course the hope is that the plants will free
sufficient O2 to take care of the animals' needs, and the light will come
from the side, not down through the duckweed. Still, if it were me, I'd
skip the duckweed.

That and, I used to take customer service calls regarding a commercially
available ecosphere, and what I learned there was that you want a very
light
animal population, compared to the plants.

I also worry a tiny bit about the pond mud. If there is stuff in the mud
that is decaying (and there does tend to be), the decay process will use
up
O2, too much decay could suffocate the animals. But I really like the
"live
cultures" aspect. So I'm torn. Go lightly on the pond mud.

Please let us know how everything goes.

-Chris


--
Chris

Chris Oinonen Ehren wrote:


I worry a bit about the duckweed. In ponds it usually signals a not very
healthy pond ecology. It cuts off light to plants beneath it, I tend to
think it cuts down on the surface area of the water, limiting the exchange
between water and air. Of course the hope is that the plants will free
sufficient O2 to take care of the animals' needs, and the light will come
from the side, not down through the duckweed. Still, if it were me, I'd
skip the duckweed.


Note that in a closed system plants can grow only as far as available
carbon (and other nutrients) allows. This is completly different from
the standard aquarium tank, where food and CO2 from the air would indeed
allow mass propagation.

The question really is which plants and animals can live together in
that little biotope, and it might help to have several species to begin
with. Some will wither, others will grow.

Appart from duck weed, there are some other surface-swimming plants with
nice "roots", like _Riccia fluitans_.

Thanks for your advice;
Limnophile

"Dr Engelbert Buxbaum" wrote in message
...
Chris Oinonen Ehren wrote:

Note that in a closed system plants can grow only as far as available
carbon (and other nutrients) allows. This is completly different from
the standard aquarium tank, where food and CO2 from the air would indeed
allow mass propagation.

The question really is which plants and animals can live together in
that little biotope, and it might help to have several species to begin
with. Some will wither, others will grow.

Appart from duck weed, there are some other surface-swimming plants with
nice "roots", like _Riccia fluitans_.