I have 2 guppies in my 30l biorb at the moment. was looking to add another 2/3 fish to the tank. what would be best? is there anything guppies dont get on with?
Look at the shape of the fins, the blue gonopodium Helen G was talking about
if you have one of each then you'll need another 1 or 2 females.
if they are both male then i would suggest getting another 3 to avoid aggression