Guppies are livebearers that originate from brackish waters. If being kept in freshwater, be sure that you have a high GH & KH content for them in order to replicate the mineral levels of their natural environment. Being that they are livebearers, these fish mature very fast and can give birth once a month. Also ensure that there is enough territory if you are trying to keep multiple male guppies without a female, as they will pick on each other. Being that they are grazers these fish eat a lot and will often pick at other fish if given the chance, so supplement algae wafers or fish treat tablets.