I have an adult male ACF and recently acquired another. They have been together about a week. Both have lived alone their whole lives. I have noticed them mounting each other, both of them seem to be bothered by it. Also, they will nip at and bite each other, especially when it comes to feeding time. They live in a 20 gallon long aquarium, so they shouldn't be stressed by the space they have. Is this normal behavior until they establish a pecking order or should I consider separating them?