Though once they saw me working on it, they wanted to participate, this was at the start my own project, not something I was doing for the children. I said nothing to them about it except that they should choose 3-liter bottles instead of 20-oz when they were allowed to go to the corner store and buy themselves a pop. This pleased them and they did not look the gift horse in the mouth.
I read more than a dozen websites, trying to sort out the best way to make the kind of bottle biome I imagined. To organize the information for my own scatterbrain, I ended up writing myself a guide and shopping list and following that instead of one particular set of directions.
The first step was to save the bottles. I was able to gather a small collection over the course of a couple of weeks and I set to, as follows.
That's the prep. After the prep, you are ready for project day. It kind of all has to be done at once, because you're working with live animals, so plan to do it on a day when you can come straight home from picking up supplies and make your bottle biome with your shoes still on. Since my children wanted to participate, and it fit in with the botany unit we were doing, I scheduled this project for our science day.
The first item your bottle needs, you can't get at a store. You must place some decomposing biomatter that has been outside for a while into the tank, a last step, but something to make sure you have before you start. A dry leaf that has clearly been on the ground seems to be the most common recommendation. I guess they carry micro-organisms that the fish like to eat. If this makes you feel a little annoyed about all the cans of fish food you've bought in your life, welcome to the club.
We had some confusion when I walked in to the store and said I needed "pond plants." They refer to them as tank plants. They wanted to know which type I needed. I was under the impression that it didn't really matter, I just needed anything green and alive in there to complete the O2 and CO2 exchange. When I told the staff that, they escorted me to the plant tank and I instructed the children (who by now had figured out what I was up to) to choose one that looked like it would fit through the top of the pop bottle.
Pushing the pond plant through the top of the bottle felt like it was going to kill the plant. Our four-year-old poked a hole right through the middle of her plant, trying to shove it in, but it lived.
Adding the snails was next. I let each of the children reach into the water, pluck a snail with their fingers, and plop it through the pop bottle lid.
Last, we added in the guppy. I scrunched up the opening of the bag, tucked it deeply into the bottle opening, and flipped it upside down so it'd pour out. The guppies clung to the plastic, though, getting caught in the creases and folds I'd created. I ended up in each case using my finger to scoop and push the fish into the bottle. One flopped onto the table. It was pretty terrible, but they all lived. The one who flopped onto the table was named Bravery in honor of her struggle.
Well. Almost anything. A couple of mornings ago, a child came running to tell us that Bravery was having babies. It turns out feeder guppies can produce up to a hundred at a time!