I have 5 guppy fry who are about 2 months old. I believe 3 of the more colored ones to be Male and the two lighter colored ones female. The two that I believe to be female have chosen two spots where the filter flows the most through the tank, and they wait for detritus worms and anything extra they can snack on or pick at to flow through. They stay in the same spot unless they spot something edible or a Male guppy tries to come into their "space". Then they will chase the Male guppies away and nip at them until they leave. Is this normal behavior? They just started doing this. I feed them once or twice a day and the water parameters are good. It's a 20 gallon tank and their only mates are 3 corydoras and 2 nerite snails who stay out of the way.