kuyper wrote:


When a breeding population outgrows it's food supply, in a small pond
I would expect it to exterminate it's food supply before suffering
significant losses due to starvation, so it would therefore end up
starving to death. For insectivores and algae eaters that's less of a
problem, because new sources come into the pond all the time. However,
it seems to me that anything which relies on aquatic plants for food
is not going to see its food supply quickly re-established. I had been
hoping to have the fish keep the plants in check, so I wouldn't have
to do any weeding; from what you've said, it sounds like this would be
feasible, and I'd like to understand how that works.

I, like you, only know the theory and suppostition......I want my new
pond to be as self sustaining, low maintenance as possible as I have 7
aquariums that need constant attention. My supposition is that you keep
omnivores in the pond that will eat both excess plant growth and any
insects or other creatures that wander in......so I'm looking at
goldfish right now....I have attempted it before but the main problem
was leaves from trees and not being able to keep up with the removal of
the dead plant matter to the point where the pond sustained frogs, newts
and other creatures but sadly not fish......so Kath's suggestion of a
"nature" pond might be what you are looking at....but then you have the
problem of pruning back plants.....



While nature is able keep a small population imbalance in check, I'm
sure it couldn't handle a large one. If I start out with too many fish
and not enough food sources, they will starve. Can you give me any
rules of thumb for how many fish and plants of a given size and type
can be supported naturally by a pond of a given size, and in what
ratios?

In my experiment I would be inclined to go for a high density of plants
and a low density of fish.....but then I am going to factor in the
possible need for more conventional filtration as and when I need
to.....My ideal plan is to have a veggie filter and heavily plant the
pond....stocking will be light and I'm not looking at keeping Koi
(although this might change).....of course the size of your pond would
be another great factor.....my step-brother has a 5 acre pond where he
raises trout (in Scotland) and the feeding and maintenance is minimal
because it truly mimics nature - so I guess in this case it is a matter
of scale again in the same way as it is with aquariums....


The rules of thumb I could find for aquaria were based upon
plants artificially supported by pumped CO2, and fish that were being
artificially fed. They assumed that the fish weren't eating the
plants, and that the plants were being trimmed by the aquarium keeper.
As a result, those densities are way too high for the approximately
balanced ecosystem I'd like to set up.


I would not like to not feed my adult fish in one of my aquariums but I
do not supply any special food for the fry and do have some survive and
some become additional feed for the adult fish. My Mbunas certainly eat
the plants but do also need additional food for their health......my
platy fry survive initially on the stuff living in the algae - but does
everyone want string algae in their display tanks? I would agree that to
sustain the level of plant growth that you would need to support a
colony of fish might need an extra boost such as CO2 or ferts.....I read
your thread on TFA with great interest (even though I didn't join
in)........but I do think that you might have more success with an
outdoor pond than you would with a closed system - it's the closed
system that is the key to the problem and unless that keyed system is
massive then you just will not pull it off.....and yes I know about
those silly eco-system ball things.....

Gill