good/fair question Dave... but you are mistaken about the wholesaler conspiracy. Really... its just a perfect/innocent example of how a lack of business education handicaps start-ups. Mind you... you don't need a collegiate degree in business to get onto a good path... just some books, free weeknight/weekend seminars at the local university business schools... various community small business outreach programs, etc.
But to answer your question specifically... "how to find wholesalers" - it is as stated above: subscribe to the industry trade journals. Its that simple. You pay for a magazine subscription, and you get monthly mags with articles and advertising about aquarium industry business. They also have annual indices of manufacturers, wholesalers, retailers, suppliers, etc.
And if/when you get just a little bit of business education... you will learn fab tips like just looking merchants in various/specific fields of commerce simply by petitioning Chambers of Commerce for public information.
Then there is attending the industry trade shows and conferences (whos dates and venues are listed in the trade mags and journals... ahem
. At such shows you will meet the wholesalers/suppliers face to face... as well as other retailers like you who are usually happy to swap info since y'all are usually from different states/local markets).
Networking.
It's simple and cheap beyond the investment of your time. Just like any other trade or industry
Well worth it.