do you think i could get away with just live rock and flow?as will be no fish or bio loadBest filtration I can think of would be live rock to start. Skimming would help, as would any form of nutrient export (such as macro-algae or a Deep Sand Bed).
Most frag out tanks I have seen tend to be large with sump filtration, or linked to the display tank so benefitting from everything on that.