I get that all the time

After lunch they went to the reptile house. It was cool and dark in there, with lit windows all along the walls. Behind the glass, all sorts of lizards and snakes were crawling and slithering over bits of wood and stone. Dudley and Piers wanted to see huge, poisonous cobras and thick, man-crushing pythons. Dudley quickly found the largest snake in the place. It could have wrapped its body twice around Uncle Vernon’s car and crushed it into a trash can — but at the moment it didn’t look in the mood. In fact, it was fast asleep.

Dudley stood with his nose pressed against the glass, staring at the glistening brown coils.

“Make it move,” he whined at his father. Uncle Vernon tapped on the glass, but the snake didn’t budge.

“Do it again,” Dudley ordered. Uncle Vernon rapped the glass smartly with his knuckles, but the snake just snoozed on.

“This is boring,” Dudley moaned. He shuffled away.

Harry moved in front of the tank and looked intently at the snake. He wouldn’t have been surprised if it had died of boredom itself — no company except stupid people drumming their fingers on the glass trying to disturb it all day long. It was worse than having a cupboard as a bedroom, where the only visitor was Aunt Petunia hammering on the door to wake you up; at least he got to visit the rest of the house.

The snake suddenly opened its beady eyes. Slowly, very slowly, it raised its head until its eyes were on a level with Harry’s.

It winked.

Harry stared. Then he looked quickly around to see if anyone was watching. They weren’t. He looked back at the snake and winked, too.

The snake jerked its head toward Uncle Vernon and Dudley, then raised its eyes to the ceiling. It gave Harry a look that said quite plainly:

“I get that all the time.”

“I know,” Harry murmured through the glass, though he wasn’t sure the snake could hear him. “It must be really annoying.”

The snake nodded vigorously.

What does 'I get that all the time' mean?
What does 'tank' mean?