I've found a few calculators online, but they don't seem quite right. For reference, the current flow rate is around 80-100 GPH. I'm using a weaker pump because a) I want to keep the wattage down, and b) my wife can't stand any "trickling" noise.
I realize that some seepage will occur around the waterfall. This is fine, as I have a substrate drainage system in place.
I'm guessing that I can go for 300gph without much trouble (except maybe from my wife). Note that the waterfall is supplied by ~1/3" tube (at least at bottlenecks in the line), which may limit flow (not an expert in fluid dynamics or plumbing, for sure).
I know this is a difficult question, but I'd still like to know your opinions. I'll use the average suggested GPH if I get enough responses.
edit: Ugh! I used you're instead of your...I need to go shoot my foot off or something.