I don't have a tank, I don't have a filter, I don't have anything. However, I'm thinking about starting an 20g aquarium and i was interested in getting a Mollie and a Guppie. My question is can I have just one Mollie and Guppie in my aquarium or should they be in groups? Secondly, I think im going to use the fishless cycle to start with and I'm probably going to have to use gravel from a potted plant. If this is the case how do I deal with the excess soil thats on the gravel? I don't know what rinsing the gravel will do the bacteria. Any help is appreciated, thanks.