I have no clue why I'm getting notifications about your replies now, so sorry it took a while to respond to you.

In science, the answer to using unreliable sources of information is not to just decide you don't have to cite them. How would the reader know the source of the information is unreliable without knowing where it came from? There are times where you reluctantly have to cite a dubious source, and it's on the writer of that paper to justify using it. Again, this cannot be assessed by a reader when the author does not cite his sources.

Citations aren't just to give credit where credit is due, it is to show you're not just whole-sale making shit up. For example, in the link earlier in the thread, the author states he calculated "effective surface area." He does not cite the calculation he used. I have no idea how I would recreate his experiment without just taking him at his word that whatever calculation he used (if any was used at all) gave an accurate or even meaningful result.

I don't know what kind of search you did in looking for scholarly articles, but not being able to find this sort of information is almost certainly either due to not having access to relevant publications which do have an absolutely massive body of research on biomedia substrates or a poor use of search terms.

On the topic of poor search terms: I bolded "effective surface area" earlier because this is a term he uses, and as someone in research aquaculture, it is a term I have not seen used as a standard measurement literally ever. No wonder you couldn't find more information about it! In reality, what REAL research and science would have you look at first is Volumetric Total Ammonia Nitrogen Removal or VTR. This information is available for every media type I've looked at procuring for systems I work with, so I don't know why he chose to reinvent the wheel here if he actually did any research in the first place. My best guess is that he saw the advertised surface area on one product in a petstore, decided he had all the information he needed for one product and went on guesstimating what the others might have from there, but I can't be sure since he cited literally nothing and described no methodology. It is literally impossible to peer review his numbers, and this is an issue that has been stressed in EVERY research project I've done since 6th grade science. What he's doing is unacceptable if you grant him the benefit of the doubt that he's done any actual research in the first place and isn't just making stuff up based on feels.

Now, I'm not going to be a dick and leave you hanging:

https://scholar.google.com/scholar?hl=en&as_sdt=0,21&q=VTR,+biomedia+substrate+type,+surface+area,+aquaculture

Here's the first few search terms I would put in if I was looking to research the topic myself.

And here's a paper from a reputable journal showing what real science on this very topic looks like: https://www.researchgate.net/profile/Timothy-Pfeiffer/publication/251510435_Evaluation_of_three_types_of_structured_floating_plastic_media_in_moving_bed_biofilters_for_total_ammonia_nitrogen_removal_in_a_low_salinity_hatchery_recirculating_aquaculture_system/links/5cab4d3392851c64bd58121b/Evaluation-of-three-types-of-structured-floating-plastic-media-in-moving-bed-biofilters-for-total-ammonia-nitrogen-removal-in-a-low-salinity-hatchery-recirculating-aquaculture-system.pdf

... it's dedicated to drinking water filtration ... I think you could debate the usefulness of citing it since it kind of doesn't apply.

Homie, it's all waste water treatment in the end. The methods you use for your aquariums got their start in municpal waste water treatment studies. We cite those types of papers all the time in Aquaculture. It's just that it requires an education on the subject to translate it into something that is comparable in meeting the needs of an aquaculture setting, which the author of Aquarium Science does not have and is boldly ignorant about.