That says it all right there. I didn't know it was the Snikster..
Yeah...what he's probably doing is "pumping". He's filling his pouch with water to "show off" to the female. This is actually a multi purpose behavior. First, it lets him show off his "capacity". The second reason is as I said above; by filling the pouch and then expelling the water, he is telling the missus that he is ready and willing. Again, the hormonal changes in the boy primes the pouch lining with testosterone, prolactin, and such to get him ready to carry. When he deflates, he sends this personalized "perfume" into the water enticing his mate. The female, when ripe with eggs will ONLY hydrate the eggs at the exact time that the male is ready. Many feel that this pumping stimulates the female to hydrate and then transfer the eggs.
One of my boys finishing up with an egg transfer. He actually contracted and sucked them in like a kid would slurp a Jello cube
Dave