Since I introduce the frog bits to my planted refugium, I notice that my originally pretty well growing water wisteria are dying and leaves are melting away nearer to the bottom. Probably due to the over growth of the frog bits shading the light.
So, I have decided that one type will be enough. Which is more efficient at sucking up nutrients? Water wisteria looks more pretty though.... But up keeping is a little more work..
Keep trimming I would say. theirs no real way to measure root absorption, but if plant A) is okay, then b) is introduced and a) withers? ..id call that a close measurement. for example, weeds in gardens are ugly but they outcompete most other plants for nutrients in the ground.
If I could I would hydroponically grow weeds in a sump. That surely would absorb any excess fertz and nitrogen.
Frogbit can easily be a pest plant*, but it also can be an effective nutrient sponge in tanks. Because it is primarily a shallow-water floater, it may shade out submerse plats, but it may well be a better nutrient sponge than many submerse plants. That is frequently undesirable in planted tanks.
Do remember that nitrate reduction from plant nutrient uptake does not, repeat not, remove or reduce the need for water changes. Plants are not a very effective in DOC (dissolved organic compounds).
*Do not flush this plant into public sewer systems, it can cause problem in the wild. Harvested plant material should be composted or buried.