Even though I'm guru in fishing, I've only ever used the Balenos Rod... (so I'm not as "guru" as I seem)  I really I'd like to participate in the fishing competition, so I'd like to know what the best rod to use would be. 

I see the Calpheon Rod/Ash Float is for chance to catch Big Fish... is that like a different category of fish than the green, blue, yellow, and reds?

Or is does Big Fish mean just bigger sizes of the green, blue, yellow, and red? If so, would it be worth using when lacking the auto-fishing reduction? Or would it just be better to stick with the Balenos and have a lower chance to get the larger sized ones?

Any advice would be appreciated. Thanks!

"Big" = blue, "Rare" = yellow, "Prize" = red.

Thanks!

But not always. In Zulatia Sea for example, yellow fish called "Readbreasted Wrasse" is also part of big fish category. At least according to Bdolytics. No idea how accurate that info is.

And can someone explain how are fish size determined? I have been fishing since update at that spot to get Readbreasted Wrasse for competition, and it all that time my biggest one is 45. Yet I see some players with size 54 and even 60.

Are those sizes 100% only RNG based, or is there some way to increase chances for catching bigger fishes?

That's what I'd like to know also... if it's all RNG and there's not a tool (rod/float) to increase the odds, then I'll just keep fishing that I normally do with only a balenos +10 and hope for the biggest catch in the process.

I did make Calpheon +10 and a Ash Float +10 last night... just to have it for whatever situation, though.

H(knowledge) -> Life Skills -> Fishing ... you can see the Rare/Big/Prize fish

People keep saying it's RNG, but I have my doubts. Fishing 24/7, and I'm far away from those high numbers.

Even spent few hours active fishing, and doing all my fishing with tirple rod, yet it seems I won't even stay in top 100 to get rewards.

Had no idea this can be found in game. Thanks for info!