Yes a sucker fish like a plecostomous(sp?) or an upside down catfish would be good. We have about 20 fish tanks in lab and each person is assigned to one although the seniors do the 4 saltwater tanks we have cause us juniors just learned how to do tanks. Um about your mollies, they are livebearers which means they give birth adn are the easiest to sex. The main livebearers whihc are guppies, mollies, swordtails, platys, and variatys have what is called a gounopodium(sp?) males have one but females don't (swords have a diferent way) here is a good picture of male molly its a little thing sticking out between its anal fin and it's dorsal fin. Hopefully that will help you sex your fish. I want an albino oscar.

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