Aphids problem!

I have noticed that a small aphids infestation has begun on my last plant. I have searched the net for remedies and first I washed the aphids down with the shower but the next day they were even more. So i went and bought some insecticide that can be used on eatable plants but still the aphids multiplied.
Last thing i tried was soapy water, i cleaned the plant perfectly i took it leaf by leaf, and in the area that i keep the plant i placed a big pan with soapy water in which i put a support to hold the pot with the plant.
I need some advice to combat these pests without further stressing the plant.
I don't know what kind of aphids they are. they have black color and are very very small. on other plants they create some sort of webs in between the leafs(at least i think they are the same kind)
Thank you!