If you only have a few of them they can be wiped off with your finger but keep a close eye on them returning. For an infestation you can either spray off with a hose and repeat as necessary or spray an insecticidal soap directly onto the aphids. Once the soap starts to dry the aphids will stick together forming a statue and therefore die of starvation! Sounds horrible I know, but it’s better than using a pesticide. Before spraying plants with soap, always test a small area before main application, as certain soaps can harm your plants.
Ladybirds are nature’s way of dealing with aphids so if you do have an aphid infestation, you will find that they won’t be far behind so try and leave them alone.
Lacewings (picture right) are another way of treating aphids and they are pretty cool to watch them do there stuff, they throw the aphid around in there mouth erratically before digesting them. You are purchase these and lady bird larvae from some garden centres and online, though they can be expensive.
Please note that you cannot use the soap after you have introduced the bios as this will kill them as well! Ants will try and protect your aphids from predators as they help produce a good food supply for them. If they think that particular plant is under threat or is becoming over populated they will transport them to a new plant! To overcome this you can put ant killing food around the base of the stem and stop them in their tracks. Sticky traps are also handy and will help catch any other bug hanging around!