A word of caution about using plastic
A word of caution about growing plants in soda pop bottles. The plastic gives off some substances that interfere somewhat with the growth and health of the plants. Most plants are not so seriously affected that they die or fail to grow. They will, however, do better in glass bottles or jars. I still keep many of my crypts in soda pop bottles and they stay alive, and even grow a little, but they definitely do better and bloom more often in glass jars. The glass jars are covered to keep the humidity high, and, thus, the difference in growth is not due to a difference in the amount of ventilation. The plastic does not seem to bother my crypts very much. In general, they seem a little deficient in nutrients and they do not respond to the adding of mineral nutrients such as nitrogen, potassium and phosphorus.
Many stem plants are similarly affected by the plastic, They don't get killed, but they do seem somewhat unhealthy looking. A few stem plants---Hygrophila corymbosa compacta and Didiplis diandra are more adversely affected. The Hygrophila corymobsa comapcta started growing, but had no internodes. I thought it was supposed to be like that, and so I did not think anything was wrong with it, but the plants began to shrink in size, until they were about the size and appearance of duckweeds. At that point, I transferred the plants, soil and water to a glass jar, and the plants recovered quickly. At first they had normal internodes, but after they got about 10 to 15 centimeters tall, they got that 'compact' look with the internodes very short. The fact that the plants started growing normally when I transferred the soil and water to a glass jar indicates that the harmful substances from the plastic do not persist in the soil or water for a long time. That is encouraging.