Recently tore down 300 litre lower light tank that I dosed product "Metricide 14" at 20ml a day at same time each day(important ) for nearly two year's.
Product(Glut) in nearly twice the strength of Excel and much cheaper by the US Gal.
Plants were mostly Anubia species,Bucephalandra,Water sprite,Crypt Balansae,Echinodorus Rose X2.
Plant's performed well with daily dose mentioned,along with once a week addition of dry fertilzers Macro/Micros, and weekly 50% water changes.
Same tank performed equally well for same period without the Glut but seldom saw Large Sword plant's throw out runner's which escaped the top of the tank with such vigor.
way less issues with hair algae that used to tip the ends of the Crypt Balansae that lay upon the surface directly Under LED'S.
I think the extra carbon source for plants from the liquid supplement's can only be a benefit in otherwise limited environment.
Will not in my view, allow for light energy to exceed capability of increasing CO2 as might be demanded by more demanding plant's.
Given short time that liquid carbon remains available for plants 12 to 24 hours I believe is quoted,,Dosing just before light's on at same time each day,,produced best result's for me .