Well, depending on the loading rates, the sponge filters may need a good cleaning every so often.

You can have too much "mulm". This is true for sediments as well as biomedia.
Things can and do get reductive if you have too much. It clogs and the reductive by products are not good for an aquarium.

You can have low load aquariums however.
These work for years without cleaning them.

Still, on most CO2 enriched systems, cleaning the mulm out every few months has a noticeable effect on the O2 levels, growth rates of the plants.
On a non CO2 planted tank, the rate of cleaning is very low however.

I think one of the key aspects in planted tanks and a good reason not to clean too much is that many of the smaller invertebrates that are hard to see or microscopic, not just the bacteria and fish alone, are stabilized and allowed to work towards cycling waste. Amano shrimp are very good shredders as well, as are most shrimp species.

Still, if you have too waste coming in, the smaller critters and the bacteria(as well as the fish etc) are using a lot more O2 trying to break down waste.

This has limits.
I generally error on the low side for bioload (less fish/easy to keep species, more shredders, algae eaters, and easier to grow plant species). I can always add more food or fish as needed, but it's harder to try and force an over loaded system to work.

Ideally, you could compost and reuse the plant trimmings.
This is something I've been toying with for sometime.
If the plant trimmings have been mineralized well prior, they work well.
If you toss a lot of plant trimmings that are slightly decomposed, they can induce algae just like adding NH4(likely because they are loaded with concentrated reduced N that breaks down in dead plant tissue rapidly).

Regards,
Tom Barr