after doing the aquarium thing for ten or so months, if there has been one thing that i have done, consistently and remarkably well, it is to make mistakes!
i hope i am not alone...
so here are my best ones:
the spills of course, lots of them.
i once got sprayed in the face with my return pump, it was a 1300 gph pump also. that happened because i was trying to adjust my ball valve and unknowingly loosened the connection to the pump itself.
i have casually left a hose in my mixing tub before and have lost 50 or so gallons to the garage floor.
and much much more.
now lets hear your failures!