Hi everyone, i'm new to fly fishing and would like to know if there are any mono lines that are used for leaders that actually sink without any treatment, as i understand that is what is required most times. thanks

Afraid it's not been invented yet!
Fluorocarbon is supposed to sink, but in lighter strengths it still need some sinkant. Maxima mono again is supposed to sink and Drennam Sub Surface green.
Even if you do find a good sinking leader/tipet line, it's still a good idea to treat with sinkant as it helps to take the shine of it.

I'm new to fluorocarbon, which is supposed to sink easily. If you use it, check the internet for knots for it, because I had trouble with the half blood knot pulling out. I also found that the knot needs tightening very gently and some saliva or it stresses.

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"Take not out your 'ounds on a werry windy day" Surtees.

wobbly face and bill. Thanks for the info, i used maxima when i coursed fish and it was a good line , brilliant for knots no curl at the end of the hook, as for the florocarbon i was'nt sure about it espeacialy as there is no stretch in the line, did'nt if it would crack of on a good fish, anyway i will store all your information, thanks, bricon