the biggest loach i have ever had is what i currently have. a weather/dojo loach at 7/8 inches. shes one big mama! like cigar sized seriously! shes an experiment im currently doin whether i can breed them or not.
the biggest shoal i have ever had was before i moved out. 30+ tiger barbs (green, normal and albino mixed) it was amazing! i miss it
My lfs (one of the if not the largest in ohio) has 12 - 12" clowns in their 960 gallon asian biotope community display tank with a huge assortment of gouramis and other botias along with some MASSIVE pieces of driftwood (45-50"). It's an acrylic hexagon with rounded edges for a nice view and it sits in the center of the store with the stock aquariums all around it. The owner had kept the clowns since he was just out of college in the '80's (his dad owned the store before him and they were originally bought at 3"). They also have a 500 gallon (standard rectangular shape) display tank with 12 - 8" discus and around 150 Cardinal Tetras. The craziest thing is that they have an automated system to do 50% water changes every other day and each type of water has its own canister which is pumped though pipes into the tanks that require each type. They use a commercial R/O DI system and have automatic feeders that dispense the pH/buffering mixes for each type of water. I saw the system in action last week as they were closing; It was crazy.