The use of sand for use in water filtration pre-dates recorded history. Sand was ‘understood’ to be a highly effective means of purifying water by the Babylonians, ancient Africans, Chinese, Egyptians, Israelis, Native Americans etc … albeit that they did not know ‘exactly’ how or why it did so (microscopic particles and microorganisms being totally unknown to them). They ‘just knew’ from direct experience/evidence that it did ‘work’ and worked well with little to no effort. That’s truly all that they actually needed to know … and in reality, that’s basically all that anyone (you) really needs to understand … it just works … every where and every time.
This is FAR from a new concept or novel technology and as such not alleged (by me) to be an invention in any way, shape or form. Sand filters remain the preferred filtration media, still in continuous use today, by for example professional aquarium managers such as at SeaWorld and Epcot Center.
Sand filtration is basically ‘fool proof’, works every time, automatically, effortlessly and effectively. Sand (Silicon dioxide e.g. quartz) does not break down, wear out or need replacing (within reason) and is basically infinitely recyclable. Even if/when it might eventually become ‘overloaded’ with organic ‘wastes’ it can easily be cleaned, flushed and reused repeatedly. And if that should ever present ‘too much hassle’ for someone, it can always be sold (as a value added product) as a soil amendment to organic gardeners, farmers in regions with heavy clay soils, golf courses and likely put to other uses.
When (medium to medium-coarse) inert sand is employed to filter ‘waste’s from aquaculture, the sand surface physically strains the suspended solid ‘waste’ fraction (particles, including microscopic) from the water, leaving it at/near the surface exposed to Oxygen and rapid decomposition. Sand has an extremely high specific surface area (composite surface area by volume) for soil microbes to attach and/or inhabit, A well-drained sand is approximately one-third pore space (atmosphere) by volume. This means that a non-saturated (drained) sand has ample atmosphere (21% Oxygen or 210,000 ppm) to support vigorous aerobic soil microbial communities.
Products of the initial ‘waste’ decomposition occurring at/near the surface migrates(moves) down into the subsurface sand with each subsequent irrigation event, where these compounds are sequentially ‘processed’ (metabolized) by multiple species of soil microorganisms. A diverse soil ecosystem develops naturally and autonomously. which progressively, biologically transforms the fish ‘waste’ products (both the solid fractions and solutes) into nutrient forms that vascular plants grown in the sand will assimilate. Plants grown in this organic-rich sand (soil) perform the function of filter cleaners by extracting their nutrient requirements from the sandy soil and thereby limiting/preventing toxic accumulations.
The sand (physical substrate) + Carbon- based biomolecules (organic fish ‘wastes’) + soil microbes + water and Oxygen = SOIL.
In Summary, the use of sand as an extremely effective and highly practical filtration media is not Not NOT a ‘new’ or in anyway a novel technology. It has been consistently proven effective for at least 10 millennia (probably far longer) and there is absolutely nothing about sand or sand filters in the digital age that can/will ever change that in the slightest. Similarly, “soil” (mineral + ‘organics’ + aerobic microbial life) is well understood to support vigorous plant growth. Removing aquaculture ‘wastes’ from water permits the return of clean water for reuse. Providing organic-rich fish ‘wastes’ along with abundant Oxygen and water to a mineral substrate (sand) will support rapid plant growth with high yields. That is what iAVs does (is).
PS: Neither gravel nor expanded clay pebbles has ever been known/shown to be an effective filtration or water purification media. … not in pre-history (assumed), over recorded history, and certainly not over the past 27 years of fraudulent nonsense disseminated at the speed of light by willfully gullible modern-primatives.