koralia seems like overkill. I like the tom dive clean micro pump for things like this. I actually use them as filters in tiny tanks, I must have 4 or 5 running right now. They make a mini version that is longer than the micro, that is adjustable speed. it's plenty to create flow without disturbing anything.
and since I'm just jumping in here, I laughed out loud at your comment about washing flourite... I KNOW I SHOULD, I know how dusty it is, and I still keep on throwing it in unwashed. takes forever to clear.