here's some shots of my 30 long that is currently a goldfish storage tank / experiemental filtration tank.
in one of these shots, you can sort of see my diy'd overflow
gravel is a 60/40 mix of sand and kitty litter, capped witih river pebbles.
plants really like it, but the gold fish like to eat plants, so I can't keep many in here
I also have some livebearer studs in here that have been removed from my main tank to prevent inbreeding.