How do I know my filter is sufficiently sized to handle my bio-load?

[Andrew_L]

I am considering building my own HOB filter as a fun project and a way to improve my filtration capabilities in my current tank. In designing the filter, I realized that all this time I've just assumed that my current filter was "decent enough" and doing a good job. My tank is mostly clear when it has its weekly water change and the fish all seem fine, but I was wondering if there are objective measures to tell whether my filtration system is doing everything that could be done. I recognize that filtration has diminishing returns with each additional layer of filtration, so while I don't want to design a filter that is too small, I also do not want to design one that is considerably larger than it needs to be for marginal benefit.

Part of me thinks that the best objective measure of a filter's effectiveness is water chemistry, but I am unsure if filter capacity is the only component of that measure or whether there are enough external factors to make it hard to use chemistry as a clear indicator. Any help would be appreciated! 

[Andrew_L]

Silly me, 10 minutes after posting this found that Cory already did an hour-long video on this topic that I must have missed in my initial bout of research. Input is still appreciated, if people have suggestions. 

Edited March 1, 2021 by Andrew_L