Updated: May 12, 2019
The natural nutrient recycling carried out between plants and animals promotes a healthier captive environment for both. However, the co-culture of flora and fauna doesn't come without its own particular challenges. Ofttimes, the most frustrating aspect of culturing plants and fishes in the same space is herbivory: grazing of the plants/macroalgae by the fishes. While entirely natural (we generally welcome natural processes in our artificial systems, do we not?), hungry vegetarians can quickly decimate all plant life within the tight confines of an aquarium or small pond.
For this reason (and some others), plants may be sheltered and pampered in a safe (i.e. fish-free) space. In a pond, this might take the form of a bog filter. In an aquarium, such a space can be provided with a refugium. A keeper will in some cases lack the resources (space, cash, etc.) for the add-on. If he or she hopes to enjoy the ecological benefits of maintaining plants with fish--necessarily keeping them in a common space--then inedible or poorly edible plant types must be selected.
These herbivore-resistant species possess various types of defenses. But, generally, they either impede grazing activity (via thorns, tough fibers, etc.) or produce noxious substances.
Though it has rather soft and delicate foliage, ribbonweed (Stuckenia pectinata) is loaded with defensive chemicals. Like the legendary chemical warrior Eurasian watermilfoil (Myriophyllum spicatum), most of ribbonweed's chemical deterrents appear to be phenols and phenol derivatives.
A fascinating study by the Utah State University Ecology Center puts ribbonweed (and its extracts) to the test, pitting it against a most fearsome herbivore, the common carp (Cyprinus carpio). Findings suggest that while its phenols were not always distasteful enough to thwart grazing, they did appear to reduce the fishes' preference for the plant.
Stuckenia pectinata is a fantastic freshwater and brackish bog/refugium plant. It thrives in eutrophic conditions. Its grassy structure creates a rich biogenic habitat for small aquatic animals such as amphipods. And, like any living, growing aquatic plant, it helps to drive nutrient cycling in recirculating aquaculture systems. But to keep them in the same holding area as fish?
It's a bit puzzling that ribbonweed isn't more often used ornamentally, as it is attractive, hardy and shares biotopes with numerous popular aquarium fishes. It would certainly stand up against the sorts of fish kept in the typical "planted" tank. It could even be used in many non-excavating African cichlid biotopes, being well adapted to survival in alkaline lake habitats (including the Rift Lakes).
So, for a moment, set aside the facts that ribbonweed can live in cool or tropical temperatures, can live in freshwater or brackish waters and tolerate a wide range of pH. For the reason that it deters herbivores alone, it might be suitable for use alongside a fairly large variety of fishes. Just as the Ecology Center paper suggests that S. pectinata could (specifically due to its ability to deter herbivores) be appropriate for increasing structural habitat in damaged lake ecosystems, the plant might similarly be used to improve water/habitat quality even in the presence of many herbivorous aquarium fish species.
Given that ribbonweed hasn't been used much in the aquarium/pond industry thus far, it'll be exciting to see what new and interesting applications it can be used for!