Hi Jonette!
About black mosquito larvaes I didn’t hear something like that. It is said about the red ones I guess. And it is a difference if you breed them yourselves or if you buy them in a shop from an unknown breeder. I had just bought white ones for my Spaerichtys. They are too big for my Paros.
The rolls are no leaves, but made from bark. I got once some peaces of barks, but I think it is not the same as leaves…
There should be more than one source for catappa leaves in Netherlands than one very expensive? The leaves last about three weeks in the tanks … I get two packs with 12 xl leaves if I go once in two or three months to my aquaristic shop in Freiburg. The pack costs 6,99, from “Hobby”. They have a bit different reddish/yellow/orange colors, so I guess they have been picked at the right time.