For my floating islands I have developed several methods. Bladderworts work quite well swimming around my pontoon. They build soon a thick layer where all young larvae get eaten before they grow too big .
The first flush before Bladderworts are thick enough I catch with nets and feed the larvae to my Droseras and Drosophyllum.
Sometimes I just changed the mortar tubs Some filtered water in one new tub. Then put one overgrown island into it. Then fill it up with the the water of the former tub with all the larvae just on the center of the islands. When the water flushes through the moss and substrate all the larvae will stay in the moss.
A quite weak fertilizer fit for carnivores and orchids.
Another solution was I caught in the spring some Notonecta glauca larvae. They are good hunters and even hunt for the mosquitos which want to lay their little eggships they cant fly away until they are adult.
Bti were another way I used.
In the end my islands have a ring of Sphagnum which closes the gap between island and tub rim. After this the water is not accessible for the flieing buggers. But the bladderworts should be removed then, if they are present.