I also added a t8 poly cover so that I can vacuum my 24" deep tank without getting my hands wet at all. How did I seal the tube to the vac head, well as always I was in a hurry so I used a lighter to melt it to the vacuum head, ****lighters can and will blow up from prolonged use******* DONT USE A LIGHTER you'll burn your fingers maybe your house. Maybe glue it then seal it with silicone, something, not open flame.
See between the barbs is a piece of silicone tube from mcmaster carr, can't remember the dura but they have similar stuff at big hardware stores.