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That is quite a question. It depends greatly on what you are dosing, and what you need to dose. Comparing different liquid supplements is usually not an apples to apples comparison.
What are you adding now, and why? For example, Seachem N is a great liquid product for dosing nitrogen, but dosing it in a tank that already has readable nitrates would have no effect on the tank, save maybe the potential for additional algae growth.
This article may help you gain an understanding of the different requirements that plants have to survive and thrive: