I have a very small pond. It is perhaps 4 x 6 feet by 3.5 feet deep. My wife does not believe my contention that the 12 inches of leaves and junk on the bottom is natural and good for it. Therefore, I need to drain it so that I can clean it out really well. What is the best method for draining this thing. I think I was told it has about 500 gallons of water.
find something you can use as a filter (a kitchen strainer should work fine) drop a hose in and syphon it out. once it starts it will drain all on its own.
By my calculations, you have about 629 gallons of water (84 cubic feet).
You’ll probably need a water pump of some type. Ask around the neighboorhood and see if anybody has one to loan you, or else it looks like you’ll have to drop somewhere between $50 and $100 at a hardware store for one. Maybe you can find a place to rent it.
To have a siphon, the pond would have to be somehow elevated above the end of the hose. It’d be great if the pond was at the top of a hill, but that’s typically not the case.
Though I’m sure one of our resident engineers will come along shortly to tell me/us about some weird loophole in the laws of physics that allow siphons to operate under different circumstances 
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Multipurpose Drill-Powered Pump
“Pumps up to 650 GPH … pushes water 99 feet
Fits a garden hose, can run dry
Fits electric drill or AC/DC motor with #10902 coupler
Pumps water and many other liquids
5 1/2in. from inlet to outlet, 3 1/2in. thick x 3in. high
With repair kit and suction strainer”
Venturi Pump
“This little gadget can pump 200 gallons per hour without electricity. It is powered by water from any garden hose. Simply connect the pump between two garden hoses and submerge it into whatever needs draining. It will lift water 8’ high and drain to within 1/4” of the bottom. Made in USA."
CMC fnord!
Drill-Powered Pump - $14.99
Venturi Pump - $12.07
CMC fnord!
Call your local equipment rental place and ask for a ‘trash pump’ and 100’ of hose. Shouldn’t cost you more than $60 and it’s the right tool for the job.
I stand corrected! And that drill pump looks pretty damned neat. Too bad I don’t really have anything to pump, or I might actually get it! 
You can also use a wet-dry vac with a waste outlet. You may need to get a longer vacuum hose depending on the layout of the property.
Some of these wet-dry vacs are designed to run like a sump pump, with constant suck/waste action. If you don’t already have one that will do this it might be time to get one. A wet-dry vac will come in handy for all manner of household stuff too.
I think HomeDepot had one last time I was there that specifically adressed the pump feature.
You don’t buy tools BECAUSE you need them,
you buy tools because you MIGHT need them.
CMC fnord!
You might want to check your state laws before draining this. Many states have strict regs regadring altering the natural environment. Something that small, you ought to be OK, but check first, because the fines can be heavy. Here in Minnesota, the Dept of Natural Resources is widely feared for this.
P.S. Your wife is probably right; that junk on the bottom is NOT good for the pond. At least, it will affect the oxygen in the water, and make it harder for fish to live in the pond.
If you have an actual sump pump or if someone can lend you one, that would probably be the best and quickest way to drain it. Sump pumps like those used for basements can usually pump 50 gallons a minute of more. That would make quick work of the pond. They cost $150 or more new however.
I don’t know if they’ll tackle the leaf issue though. Would your typical sump pump have trouble getting clogged in such a use?
I think most of the solutions offered here will fail due to the clogging issue. A trash pump is what is used on construction projects to empty excavations. They are designed so that they do not clog easily. That’s why I said it’s the right tool for the job.
I checked with my local equipment rental place and it’s $28/day to rent a 2" diameter trash pump, so much less than the $60 I mentioned earlier.
Of course, draining the water makes it harder still for the fish…
I do have a wet dry vac, but it does not do well when the end is totally submerged as in when I tried to vacuum up the bottom of my hot tub. Actually, I just want to get the water level really low, so I can hop in with my swim suit on and manually remove the crap, if need be, I can elevate the pump so it doesn’t clog. I really like that drill powered model. I wonder if Home Depot or Lowes carries it.
I have never drained my two 8’x8’x3’ pools for fear of killing the various newts, turtles, frogs and other creatures that live in it. I’ve used a large net to carefully remove trash from the bottom although much remains. 
The goldfish and Gambasia don’t seem to mind.
Anonomously ring the police and tell them that you saw someone furtively dump something in the pond. You aren’t sure but it looked like a sack with something in it or maybe a gun. After the police have drained it just scratch your head and look puzzled.