--- In homemadebiospheres@yahoogroups.com, the_jon_person <no_reply@...> wrote:
>
> I am working to start my first biosphere to keep myself occupied during the
day and I have a couple questions on what I should be adding to it.
>
> I can not decide on the number of plants I should add to my biosphere, Does
anyone know about how many leafy plants (please include sizes of plants in your
answers if possible) should I add for every, lets say, cubic foot of soil?
>
> Also, Would I be okay with only bacteria and plants in biosphere or should I
add a few critters to help balance out the O2 CO2 etc. levels.
>
> Thanks
>

There are no hard and fast rules regarding number of plants per square foot or
such. Different species will have different needs and different conditions will
also set limits on the number of plants you can have.

There are also different philosophies regarding density of planting in a closed
system. I prefer to underplant my biospheres where others prefer to pack the
biosphere full of plants.

Animals aren't really necessary fo a biosphere and plants and bacteria will be
fine and provide plenty of their own O2/CO2 to cycle. Animals require more
specialized conditions by and large and are more sensitive to disruptions.
Snails are often pretty tough though as mentioned earlier.

A plant only tank will often last for months to years depending on the set-up
but in my experience most biospheres that include animals run down to brown
residue within a few months unless they are very specially designed, and usually
this means much more complicated and expensive than the average hobbyist
aniticpated.