Make it more worth your time by spending an hour or two killing worms first. Use the Zinc Ores you get to make Brass Ingots and use the Flint Stones you get to make Glass Fiber. You can then use them to craft your own minnows. It'll only cost you the price of the crystals so every fish you hook up is a profit.
Inevitably any way of making money that doesn't rely on fluctuating AH prices or waiting for people to buy your product or item is going to be popular: more so when it can so easily be botted.
Whether or not it's worth it, I'm not convinced. On Lakshmi a stack of Brass Ingots is 40k, a stack of Glass Fiber 30k so you're looking at 70k for 12 minnows. I don't know what the success/line break ratio is like with Hakuryus but you'd need to fish up 7 just to break even making your own minnows - you could just sell the materials for 70k if you're not going to fish up more than 7.
Seems like Watusa's idea is the best or just finding another source of income except for those days where you get lucky and find a billion minnows waiting for you at the guild NPC.