My husband is quite good about it. My tank is completely mine and the work is also all mine, but he's quite aware of what's what in the tank. He goes with me to all the shows and club meetings/events, and knows the coral names pretty well. Sometimes I'll buy the things he likes, but I do retain veto power. :p
We do have yours, mine, and our bank accounts, and the cash I spend is my own. But he's almost always aware of the cost of things and let's me do me. :)
On the rare instance I'm traveling alone, he'll feed and keep an eye on things. If something went wrong, he'd know what XYZ thing to tell me about, but wouldn't necessarily know what to do with it without some instruction.