Urgent help needed with graph drawing!!

I have to draw a graph to compare the predation of two species over time..

This is the data I have:
Asterionella: (no. colonies ml-1)
Control = 12400
6hr = 5100
12hr = 7600

Chlamydomonas: (no. cells ml-1)
Control = 50200
6hr = 33400
12hr = 7500

I have no idea which sort of graph is best to use as one is for colony count and one is for cells and I'm getting myself all in a muddle

I initially did in in a bar chart form with a bar for each species next to each other with the time along the x-axis - is this the right format to use!? I just struggle with choosing the right sort of graph initally so any help in appreciated.