Kaysie, I've never heard this. In fact, I've been told that as long as the media remain submersed it can survive for several weeks. How do the bottled 'jump-start' bacteria colonies survive a 6+ month shelf life? I'm talking about ones that actually contain viable bacteria and work, like bio-spira/safestart, Dr. Tim's, and a couple others.
Perhaps Kaysie didn't mean 'die', per se.
There are two main types of bacteria in the tank: aerobic and anaerobic. The former is desired. Aerobic bacteria rely on a constant supply of oxygen in order to proliferate and survive. Thus, by turning off the filter, the water is no longer being agitated which, in turn, negates (to a certain extent without taking into account natural gas exchage, i.e. diffusion) the gas exchange between the environment and the water. This is also bearing in mind that there isn't that much dissolved oxygen in the tank (with the exception of the temperature of the tank). Turning off the filter will also increase the "bioload" to the tank. A tank with a heavy "bioload" will inevitably have less dissolved oxygen.
Most people have claimed that
Biospira works, but I have never tried it. However, it is certainly better the "couple others" that you are referring to, namely
Cylce.
Cycle contains bacteria in a bottle much like
Biospira, but it is kept at room temperature. When you purchase the bottle, you have dead bacteria in a bottle. So, you have effectively paid ~$12 for a bottle of dead bacteria, which will only add to the "bioload".
Biospira, on the other hand, must be kept in the fridge. There is more dissolved oxygen at lower temperatures, which means the aerobic bacteria are able to survive.
Jay.
