Overstocking: Guilty as charged.
Right now in the 75:
2 8-10" Geophagus altifrons
7 3-5" Thorichthys pasionis
10 2-3" Columbian tetras
10 2-3" Buenos Aires tetras
1 large blue angelfish
6 3-5" Biotodoma cupido
10 3-4" Corydoras robustus
2 3-5" yellow Ancistus
3-5 3" Corydoras CW036
6-8 assorted small Corydoras similis and melini
Running an Eheim 2028 and a 2227 plus an Emperor 400. Obviously a 125/150 would be a better fit, but its been like this for several months. When I get my 100 filled the Geos and Biotodomas will have their own digs.
Find that a few species in a tank as opposed to many has several advantages, among them lower maintenance, healthier and more well-adjusted fish, higher likelihood of spawning and other 'natural' behaviors, and potential for an overall equliibrium bordering on equanimity wherein the tank just feels right and less like a tank and more like a habitat. Have a 55 with 5 sub-adult discus, one blue angel, a pair of Keyhole cichlids, some diamond tetras and a couple Corydoras herds distributed around two huge java moss enshrouded driftwood pieces and pennywort strands and one can almost imagine that somewhere in the world that's what it really looks like. Very mellow, very restful tank.
Think there may be a tendency among neophytes and ardent types to amass lots of fish/species very rapidly. I just hit the point where I'm actually decreasing rather than increasing the number I have and starting to spin off more species than I bring home. Nothing wrong with them, but now that the headlong expansion has stopped, it's about fine tuning the aesthetics, maximizing spawning activity and aiming for some sort of balance/dynamic equilibrium within each tank. As I already have that with the filtration and the lighting, it reminds me of all the work that initially goes into creating a garden so that eventually one has the leisure to prune, harvest and simply enjoy it.
"Drink deep, stay wet and spawn often." - Tony Horos, July 23, 2011, ACA Convention, Washington, DC