Pop Bottle Aquarium/Terrarium Assignment

[Kurien]

Hello all, so for school the teacher assigned this project. He or she says that the purpose of this project is to "consider the delicate balance of every biotic and abiotic element within a closed ecosystem" (paraphrasing mine).

First off, could you please tell me of any science based, particularly biology based, forums where I might get the best answers?

Basically, the assignment consists of two things: making a two-tiered terrarium/aquarium thing out of two 2-liter pop bottles, and then making observations of the T/A over a two week period. Elements required for the project are


2 two liter pop bottles
Dirt or potting soil
Gravel
Drinking straw
Shoe Lace
Small terrestrial plant
Aquatic plant
One fish


Some thoughts:
So the total volume of the T/A is less than 2 liters.
The whole thing is meant to be sealed with tape, so no feeding the fish or adding fresh air to it.

It seems my main problem is that I need to match the metabolic rate (oxygen consumption and carbon dioxide emission) of the animal to the photosynthesizing rate of the two plants, or else I think everything in the T/A will die quickly. Where can I find information on these factors for plants and animals I could acquire easily from a pet store or greenhouse?

Other problems are supplying the fish with food already in the container which it can feed on. Presumably, we are supposed to choose a herbivorous fish and an aquatic plant the fish will eat, both of which fit in a very small space.

I would appreciate if anyone with any biology knowledge could help me with this. :smallsmile: I was kinda annoyed how the teacher hardly gave a single clue on how to do this properly.

[Brother Oni]

The term you're looking for is biosphere (http://en.wikipedia.org/wiki/Biosphere) or ecosphere (http://en.wikipedia.org/wiki/Ecosphere_%28aquarium%29).

There are a number of hits for 'homemade biosphere' on google and there are commercial ecospheres available (although the exact contents of which are not disclosed by the manufacturers for obvious reasons).

Most of the advice I read advise against using fish when starting out making biospheres since they have a higher metabolic rate and less tolerance to adverse conditions.
You could try having shrimp and a small fish that subsist off them in a saline environment, rather than sticking with a herbivorous fish.

[Savannah]

Do NOT use a fish unless you have extensive experience with aquariums and biospheres. Fish are hard enough to care for properly in large aquariums with constant water flow/filtration/aeration and daily care. Oxygen is going to be one of your smallest issues -- the waste of the fish will build up and kill it in short order, even with a plant trying to absorb some of it.

Your teacher should not be setting an assignment that will almost inevitably result in the abuse and death of a living being (multiple living beings, in fact, since I assume the rest of the class has the same assignment). The only way I could see this working is if the teacher is providing close guidance to ensure that every biosphere works as intended. Otherwise it is quite simply animal abuse. I strongly recommend that you speak to your teacher, and your teacher's boss, if necessary, to get the fish aspect of the assignment removed. Alternatives include using just plants or using a computer simulation.

[Kurien]

Thanks for the replies.

BrotherOni: I probably should have just used the word biosphere, as it's the term my teacher uses, but didn't because it didn't...seem descriptive enough? :smallconfused: I'll use that term now.

Earlier, I asked him or her if I could substitute the fish for an aquatic snail, or some other invertebrate, and they seemed fine with that, but I don't know anything about how to care for them.

Savanna:

Yeah, I'll talk to my teacher, and call him or her out on the questionable nature of this assignment and try to get the animal aspect removed. It may be in vain though, because we're expected to make the biospheres this Monday, so everyone will probably have bought fish by then.

I felt uneasy about it when we got the assignment description. The teacher really didn't give us much instruction. He or she just gave a few suggestions on what kind of plants and animals to get ("beta fish are pretty tough", "use a clipping from a house plant" O_o). Come to think of it, she or he didn't seem like they expected many of the biospheres in this class to live much more than a day or two, let alone two weeks. I mean, I think that this project was apparently done last semester, so she or he should already know how successful it was.

It would be loads better if we could do this all in a computer sim, I'll definitely tell my teacher that.

[Savannah]

Yeah, an aquatic snail probably has a better chance of living out the experiment than a fish. I don't know tons about their care, though. Actually, a terrestrial snail has a pretty good shot at making it, so maybe that would work?

If you absolutely must use a fish, a betta is indeed probably your best bet. They breathe air from the surface, so you don't need to worry about aeration. They're insect eaters, so they won't be eating much of the plant, but they should be able to make it quite a while without food (not sure about two weeks, though), and the lack of food will help with the waste buildup...but still, I wouldn't give it good odds of survival. (Don't forget to buy dechlorinator for the water.)

[Lappy9001]

Yeah, an aquatic snail probably has a better chance of living out the experiment than a fish. I don't know tons about their care, though. Actually, a terrestrial snail has a pretty good shot at making it, so maybe that would work?

If you absolutely must use a fish, a betta is indeed probably your best bet. They breathe air from the surface, so you don't need to worry about aeration. They're insect eaters, so they won't be eating much of the plant, but they should be able to make it quite a while without food (not sure about two weeks, though), and the lack of food will help with the waste buildup...but still, I wouldn't give it good odds of survival. (Don't forget to buy dechlorinator for the water.)Betta fish can be incredibly hard to kill, which is probably why Wal-Mart often stocks them as the only available fish in pet sections. Granted, I can't say anything for quality of life, so I'd second using a type of brine shrimp. Sea-Monkeys maybe?

[Helanna]

Thanks for the replies.
Yeah, I'll talk to my teacher, and call him or her out on the questionable nature of this assignment and try to get the animal aspect removed. It may be in vain though, because we're expected to make the biospheres this Monday, so everyone will probably have bought fish by then.

I had a very similar project once, for basically the same reasons your teacher gave. We didn't have to have fish though, the only requirement was that it have both plants and animals. We definitely didn't have to buy anything for it.

My partner and I just filled the two-liter bottle partway with some dirt, then dug up a clod of grass/weeds and put that in. Then we added some crickets, earthworms, and pillbugs. Everything survived and were happily released two weeks later, and I actually enjoyed the project a lot.

[Coidzor]

I believe crickets and mealworms are the go-to animal component for beginner self-sufficient biospheres.

As for aquatic snails, as long as the water is good for them and there's some manner of food source, the things get along quite well. I had some actually take over a tadpole and minnow aquarium I had as a small child to the point where we watched in morbid fascination as, after we evacuated the fish and amphibians the snails just produced layer upon layer of themselves coating all of the surfaces of the aquarium. Granted, these were North American retention pond snails, so I couldn't tell you the species.

[Kurien]

I'm probably going to get snails and hope for the best. I think snails are either algae eaters or scavengers, so I can't say I will be able to supply them with food. When I went to the pet store, they said that algae need at least 1 week to grow before introducing fish, which is time I don't have. I could try using a food block, but I suspect the dissolving minerals are detrimental in such a small environment.

I considered brine shrimp, but I assume brine shrimp require salt water which may not work...

See, unlike Helanna's project, this one is extra complicated because the biosphere is supposed to have soil, a land plant, water, an aquatic plant, and an aquatic animal. I think that discounts any land based animals, so crickets or mealworms are out, but I'll check with my teacher to see if the project could be modified.

The water from the aquatic half of the biosphere is supposed to hydrate the soil for the terrestrial plant, hence why salt water may not work. I don't know of any plants I could get in one day which tolerate salt water.

Another thought: since it's winter here, I doubt the biospheres will receive sufficient sunlight to keep the plants healthy, and my teacher made no mention of using artificial lights. Also, any invertebrates are difficult to find outside in winter, so I will have to buy the animals.

[Savannah]

The snail should be able to eat on whatever aquatic plant you use (note that most aquatic plants need LOTS of light....a java fern is probably your best bet for a low-light plant). Don't go for saltwater -- the general advice is to avoid saltwater tanks less than 30 gallons, as it's hard to get the correct mineral balance in smaller tanks (it's a lot more complicated than dumping salt in....well, except for brine shrimp, where you put in way more salt than anything else can stand).

If the water is hydrating the soil, try to make sure that the container with the soil isn't completely covering the water surface -- you need some way for oxygen to get into the water.