TPhyllis and Jim wrote, On 19/05/2007 18:48:
... The population of fish (and plants) is self regulating depending on the
available resources.


Gill Passman wrote:
...
The problem with attempting a self-sustaining aquarium is that it is a
closed system whereas nature will take over with a pond. A pond will
attract wildlife that will become a source of food for the fish and
other creatures living there. An aquarium will generally only have what
you have introduced. Because the area is enclosed it becomes very
difficult, if not almost nigh on impossible, to sustain sufficient
foodstuff to maintain without supplemental feeding. In a pond, nature
will supply the foodstuff.

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.

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? 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.

We once got the pond down to one goldfish.
(We've had two fish adoptions where we gave
away fish.) From that one goldfish and four
introduced koi (to take care of runaway snails)
we have had many generations and I see baby
fish all the time. The other day I noticed a lot of
damselflies laying eggs in the hornwort. Whenever
the water level goes up the fish spend a lot of
time policing the edges hunting down insects.
We seem to have gnats hatching from time to
time. Snails reproduce in the waterfall pool and make their
way into the pond where they don't last very long.
In my fishless ponds I'm always amazed at what
shows up - rattail maggots (the larva of the dronefly)
is one of my favorite discoveries. I'm sure that those
wonderful critters get eaten in the fishpond.
The fish seem to spend a lot of time mowing substrate
algae and the critters that live therein.

k :-)

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

"kuyper" wrote:

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? 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.

The main problem I see with setting this up is that the fish will breed,
which will bring you to your scenario of too many fish and they will starve.
If you want something natural AND low maintenance, omit the fish altogether.
Then you don't even have to be concerned about your water parameters. Along
will come the dragonflies, frogs and birds. If you have mosquitoes, you
could introduce a few gambusia that will deal with them. Of course, they
breed like guppies. Depending on where you live, the county vector
control will pick those up for you.

FWIW, I don't think there really is such a thing as low maintenance pond.

San Diego Joe
4,000 - 5,000 Gallons.
Koi, Goldfish, and RES named Colombo.

On Tue, 3 Jul 2007 17:52:41 CST, San Diego Joe
wrote:

The main problem I see with setting this up is that the fish will breed,
which will bring you to your scenario of too many fish and they will starve.
If you want something natural AND low maintenance, omit the fish altogether.
Then you don't even have to be concerned about your water parameters. Along
will come the dragonflies, frogs and birds. If you have mosquitoes, you
could introduce a few gambusia that will deal with them. Of course, they
breed like guppies. Depending on where you live, the county vector
control will pick those up for you.

FWIW, I don't think there really is such a thing as low maintenance pond.

San Diego Joe
4,000 - 5,000 Gallons.
Koi, Goldfish, and RES named Colombo.

There may indeed not be a true low maintenance pond, but there can be
a no maintenance pond, as in neglected pond. I know, because I have
one. Well, three, actually, but one close by the house that I really
neglect. The others are just victims of passing neglect. I have no
idea what the pond by the house started out as, but when I got
involved it was a garbage dump. I lived with it that way for a year,
then got some heavy equipment to haul out the junk. I was left with a
large mud puddle, which I guess is better than an overgrown junk heap.
By the end of the year it was a mud puddle with weeds. It isn't the
fastest way to go but it seems to work out in the end. I've seen a
bunch of critters, from egrets and ibises (ibi?) to a Florida
softshelled turtle to a water snake named Bob (though I haven't seen
it recently). As for the frogs and dragonflies and such, "if you
build it they will come." At least that has been my experience, and
they moved in long before I thought they would. As far as mosquitoes
go you can just get these "mosquito dunks" that contain a bacteria
that gets the mosquitoes if you don't want to fuss with fish. I don't
use either, though I've used both in the past with excellent results.
I don't have much of a problem with mosquitoes, I'm not sure, but I
think the dragonflies and frogs get 'em. I've got oodles of both.
--
Galen Hekhuis
Hell hath no fury like a bird in the hand

"San Diego Joe"

FWIW, I don't think there really is such a thing as low maintenance pond.

Sure there is... when the water level goes down,. you need to do maint.
work..


--
Gareee
(Gary Tabar Jr.)

Fast growing plants grab nutrients and eventually out-compete the
algae.

Jim