That would depend on the fish that you plan on putting in your tank. I have an Eheim 2217 (264 gph according to the specs) on a 20L tank (30 inch) but it is heavily planted so flow drops pretty quickly. And the fish do fine in it as long as my dwarf gourami doesn't swim directly in front of the output. On heavily planted tanks, 10x flow is often recommended to make sure that CO2 and nutrients get evenly distributed around the tank. But fish like angelfish or betas need slower flowing water so high turnover may not be great for them. But you shouldn't be keeping in angels in a 15g. And, besides, many higher-flow filters allow the flow to be reduces manually.
So short answer: it all depends on what you are doing with you tank!
And welcome to the forum.
