Remove small and underweight LMB till your arms won't move...lol

Once you get an LMB catch rate down to 1-3 an hour, you'll be catching much larger LMB.

I'd want to treat the milfoil and chara before adding fertilizer if it were my pond!!! Just be careful not to kill everything at once, or it could cause an O2 crash as it decays (the decay will fertilize a lot too)