it's a good question, however they tend to do fine with each other, i have guppies and angel's together, and they get along very well, though they keep their distances from each other: Guppies whether people know it or not are a semi-aggressive species as are angel fish. i have two types of guppie right now, the mosquito eater [very tiny and the angels leave it alone] and fancy guppies which the angel's leave alone. i actually see the angel's chasing each other around more, but yes they should be fine together but as with any other fish non-agressive or aggressive, remember no matter what species there is always the likely hood that they might attack each other.