Grow media in hydroponics, aquaponics, or any other soil-less system is present primarily to give roots something to hold onto and remain upright, but be easily separated from roots when the produce is ready to harvest. The ideal grow media should be smooth and moderately lightweight, pH neutral, non-degradable, and offer plenty of surface area. Why surface area, you ask? A critical element of the aquaponics nutrient cycle is the presence of certain types of bacteria that break down fish waste and convert it to nutrients accessible by the plants. Bacteria are microscopic, and millions are required, so they need plenty of space to grow and multiply. There will be some in the biofilter, of course, but ideally, far more will take up residence in tiny nooks and crannies throughout the system. So grow media that is formed of a material that is highly porous on a microscopic scale will permit bacteria colonization while resisting intrusion of roots and other organic bits.
One lovely combination to pair with houseplants in an aquaponics system is ornamental koi. Koi aren’t tasty fish, so they’re not raised for food the same way tilapia is, but if your primary goal is to grow beautiful ornamental plants, koi could be an excellent counterpart. Koi are hardy fish and can adapt easily to a range of conditions, so pairing them with the requirements of specific plants shouldn’t be a big issue. Koi live for a long time and have engaging personalities, so you may come to regard them as your plant care partners, contributing their own beauty and tranquility to your space as surely as your plants do.
