Eh, check my balcony planter, no w/c, no filtration, not even a light.. nothing but dirt and plants and platies + cull shrimp and snails. Clear water, ph7 / 0 0 0. 500 tds though (I think from aquarium salt I added months ago, no point really), but fauna are still thriving, even in 90-100F weather.
I usually don't feed since there's bugs and scuds, when I remember I throw in a ton of flakes, no water condition changes. Mangrove roots uptake ammonia like no one's business, dead fishes don't even have a chance to convert down to nitrates, though I haven't see any deaths since the first week of setup, just multiplication.
That said, flow is GOOD, it helps to evenly distribute the dissolved particles (nutrients) for the plants to uptake, and dead matter to break down more quickly. Light is also good, but only if you have sufficient plants and CO2 (injection or fauna) to support the level of light to outcompete algae.