A planted tank which copies some reef tank methods?
I've been in and out of the hobby for over a decade, running both planted tanks and reef tanks. Lately I have been thinking about how some aspects of reefkeeping could be applied to the freshwater hobby.
Use of a Fuge: I know this technically is not required for nutrient export. In actuality, rapidly growing plants, even in a low-tech tank, often absorb all of the ammonia before it even gets converted into nitrates. But a secondary use of fuges is often to culture live microfauna for the main tank. I've had small ostrocods and the like grow in small planted tanks with no fish, albeit not at high densities. Maybe we could use a refugium model to allow for higher densities?
Wider use of Inverts: Obviously the freshwater side of the hobby does have some inverts - mostly ornamental shrimps and snails - but this is relatively limited when compared to the fauna in a reef tank. Obviously some of this is just because there are a lot less orders of invertebrates which live in fresh water. Some is because a lot of the aquatic roles are taken up by insect larva, which cannot be kept in tanks. But I can't help but wonder if some practices - like say the conscious introduction of blackworms into the substrate - would help to provide tanks with more stability through greater biodiversity.