Mark,
Its cool man. And things vary so much that anything is possible. Me, I'm at a zoo. We don't buy animals from commercial wholesalers. We needed string rays, they came from other zoos and aquariums. And the local marine bio professor took students out and collected some, in conjunction with FWC. The have their own boats at a dock behind the school.
And we provide FWC with about two acres and a couple of office trailers on our property. They keep boats and trucks and marine mammal rescue trailers here. Plus were on the river too. In 2014 were building a 100k gallon manatee rescue facility. All that will belong to me unfortunately. Manatees eat a lot and most of it comes out the other end. But I have experience with mammals dumping buckets of $#!+ in the pool. Were designing for 6, means will have about 10 manatees sometimes.
We do get and give animals for free, even things you could trade for a nice car. But we buy outright also. We bought penguins for $3000 each from SF zoo. (is everybody here from SF?) They are worth about $5k. We got a couple for free and we bought from other zoos. But we don't buy any animals or fish from the normal commercial routes.
We buy equipment and consumables and food from the normal places. Normal for industrial equipment or fish farmers of big swimming pool operators. But we can not buy anything ever from private individuals. Admin wont let us buy a single shrimp unless your a company.
GreshamH,
You must be a company then. I guess you were meaning you used to be a livestock wholesaler. And now your a frozen stock wholesaler

So you sell to a ton...by the ton? For us its actually a ton and a half, at a time. Fish, shrimp, squid all comes frozen on pallets. Fresh water food pellet comes from big wholesalers. Almost nothing comes from one guy with a business license.
I would like to refrain from saying where or who I am. You will be able to figure it out eventually though. I want to be able to talk freely so I can talk about companies and equipment. We get the frozen stuff mostly from Bionic Baits. Its a big company with delivery trucks up and down the east coast supplying zoos/aquariums and bait shops. I think it might be a surprise for some that we buy food shrimp from a bait company.
Don Quixote
My point through all of this, the big fish don't buy much from the little fish. But it does happen some. The big fish is big now from trying when he was a little fish. It never hurts to give it a try. When it doesn't work, try again someplace else.
--John