Hi there,
Lily Pipes are tricky.. cause it depends on too much factors.
I used to have Cal Aqua, Blau, ADA Lily Pipes and for now i have AquaRebel Lilly Pipes and these are the most effective i experienced so far.
https://www.aquasabi.com/aquascaping/filtration/in-outflows/aqua-rebell-glass-inflow-if4-17-mm
First of all, the Aqua Rebel Inflow as 20 suction grooves/entrys for water being sucked into the filter. So the filter doens´t loose any power suction. Compare to ohters where you have no more then 10 suctions. If you don´t loose power suction then the outflow as well will not loose it.
The Inflow you insert image is also a pretty good one. But still has a major defect. As the below suction grooves are separate from the above the filter looses a bit power. Cause by the time the three above suction grooves are sucking water the other 10 below loose their efecct and you will not have too much water being sucked down there. Still it all depends also on the filter power of course..
Going into your problem:
I believe It all depends on how much water you have in the tank after those couple of days. The day you do WC you filled with water till a level apropriate for that effect. After a couple of days or more, your water evaporates so the level is not the same and the Lilys loose their effect.
Make a mark on the glass when you do WC and have that effect and by the time the effect is gone look at the mark on the glass again. You´ll find the water level is minor.
Still another thing.. i believe you´re trying to do Aeration with the Lily Pipes. I reccomend not to.
Simple point the Outflow to the difuser and have enough flow down there
😉 The Lily Pipe Inflow will do the rest.
Don´t mind at all with that aeration stuff ..
If you´re watching to much bubbles at the top water and/ or water with a kind of oil surface than you can be sure your filter is not aprropriate or not well assembled. Try reduce tubes extension (Water weight in it - Phisics) or insert the originals tubes cause your lilys are reducing power filter.
And don´t try "Skimmer" cause by that way you´re not solving an issue but only covering it
😉
Big hug.