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Re: third grade project
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SteveNicol
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Joined: 16 Jun 2009

PostPosted: 2009.06.18(Thu)9:55    Post subject: Re: third grade project Reply with quote

...I don't recall exactly where I read this, so maybe some of you folks can help me out. The story goes something like this:

The first day of school, a third day class is given a fish tank for a year-long science lesson. They are to show that the fish tank can become a closed eco-system of fish and plants that needs very little maintenance: fish food and water additions, that's it.
The 9-year-olds succeed by "growing" a closed, filtered system of fish and plants.

Where can I find the story of this 3rd grade experiment?
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diademhill
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Joined: 18 Apr 2007

PostPosted: 2009.06.18(Thu)11:08    Post subject: Reply with quote

It is a myth - this cannot be done.

I have heard of reported sucesses but in each case there was "cheating".
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UncleWillie
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Joined: 26 Nov 2007
Location: Georgia, USA

PostPosted: 2009.06.18(Thu)17:10    Post subject: Reply with quote

diademhill wrote:
It is a myth - this cannot be done.

I disagree. You are not creating a self-sustaining one, you are creating one that...
SteveNicol wrote:
needs very little maintenance: fish food and water additions, that's it.


Look up Walstad tanks. In short, her methods include useing soil under gravel as a substrate, a lot of plants, and a bit of water movement. The fish waste and soil provides food for plants and they (and bacteria in the soil) filter the water. A simple sponge filter will add water movement to keep the plants happy.

Only problem is tank size. If you give 3rd graders a bunch of 5 or 10 gallon tanks, water quailty will be hard to deal with anyway.

You can always let them set it up so that they can see the food chain. Adding soil and plants. Add detritus and all the tiny critters, rotifers, daphnia maybe even scuds. Then they can add a few fish, blah blah blah, you get the picture.
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Shai
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Joined: 09 Jul 2006
Location: Calgary, AB

PostPosted: 2009.06.18(Thu)17:23    Post subject: Reply with quote

I think the problem with the description is
Quote:
a closed eco-system

Obviously it is not closed if you have to provide
Quote:
fish food and water additions

Otherwise, the project is basically what everyone on this forum already does. : )
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UncleWillie
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Joined: 26 Nov 2007
Location: Georgia, USA

PostPosted: 2009.06.18(Thu)18:27    Post subject: Reply with quote

Haha, Good point Shai! I didn't consider that it wouldn't actually be a closed system. Yep, I guess the only difference is that some of use do a gravel-vac every once in a while Very Happy
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diademhill
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Joined: 18 Apr 2007

PostPosted: 2009.06.19(Fri)2:02    Post subject: Reply with quote

Even in Walstad tanks you prune and feed the plants.

I go back to before filters became commonplace. Big tanks with a few small fish can be minimal maintainance but you can't have a"closed ecosystem", that is the myth.
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Arturo
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Joined: 13 Jan 2009
Location: Wisconsin

PostPosted: 2009.06.22(Mon)16:05    Post subject: Reply with quote

my neighbor made an ecosystem with two 2-liter bottles and the bottom had elodea, 2 snails, male and female mosquito fish(don't know the species. he said the elodea "fed" the fish but they shortly died after he brought it home. probably from high nitrates or starvation.
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Axelrodi202
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Joined: 25 Jul 2008
Location: New Jersey

PostPosted: 2009.07.03(Fri)18:29    Post subject: Reply with quote

Actually, it is possible to have self sustaining tanks. But they require a lot of research and caution, and are probably not something even a fish addicted third grader could do.
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DF Bobo
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Joined: 23 Jan 2006
Location: Canada

PostPosted: 2009.07.03(Fri)20:13    Post subject: Reply with quote

not really. theres always outside factors. if we took the amazon river and seperated it from south america, the river would not be self sustaining. theres always outside factors and you cannot successfully maintain a completely closed ecosystem long term.

arturo: mosquito fish are as the name suggest: they're pretty much carnivorous and they would NOT eat elodea. elodea is not a pleasent thing to eat for any fish.

as for walstad's tanks, even they require things like water changes, albeit not very frequently. the whole low-tech setup is built on a system of low water changes and is probably as close as we can reasonable get to the "balanced aquarium" concept of the olden days.
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Ciklido
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Joined: 06 Aug 2005
Location: Ontario, Canada

PostPosted: 2009.07.03(Fri)21:37    Post subject: Reply with quote

IT IS IMPOSSIBLE TO HAVE A SELF-SUSTAINING AQUARIUM.....not even the biosphere scientists could a achieve a terrestrial selfsustained ecosystem which is less fragile than an aquatic system. Why is it imposible because we will need TECHNOLOGY to have filtration and to move the system in some direction and why cannot it be self sustaining?, because that technology will always need energy from some source to drive the techonology and that energy source is always bigger than what the technology can output, if we use a waterfall to power a pump that can pump water back up, the water will fall but there will never be enough efficiency to equal the input energy so as to create a selfsustaining system. Unitl our techonology is SUPER advanced so much that our technology is 100 % efficient, we canot create a self sustaining system. (of course we have sunlight and such but one could argue "self -sustaining")

In terms of aquariums, we have to create a filtration system that drives water in one direction and transforms potential and chemical energies into mechanical and chemical once again. its more to do with developing a filtration system/cemical balance
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