Tropical fish Importer / exporter that specializes in Central & South American cichlids, as well as Characins, catfish, pleco, and other rare or unusual species from around the world.
I have purchased from all three. All three have excellent packaging and customer service. Never have I received anything but quality fish from all three.
The only drawback to any of the three is that COTA has a $100 minimum order. The other two don't have this so you can order a single fish and have it shipped if you want.
I like Wet Spot because they are out of Portland, OR and Im in WA so its cheap overnight for me. But their shipping prices are not outrageous anyway so not too bad. Same with Imperial that I linked, shipping prices still affordable if you meet their minimum which is not too bad. With some of the online companies you will easily drop over $100+ just in shipping overnight, so unless its something wild caught or rare, I tend to go with the ones with affordable shipping rates.
I would also recommend Southeast Exotics and Tropicals. You can find them on Facebook. Fishfarm (Ken) posts his stock there and also on Aquabid. I just received some F2 Midas from Ken and they look really good. He was great to work with.
I've also purchased from TUIC and COTA. Both have been great and would highly recommend them as well.