What is your filter setup? Does the filtered water run back into the pond with any kind of splash, such as a waterfall? If so you probably don't need those underwater "oxygenators", which can be more trouble than they're worth (as you have already found out!)
A fountain or waterfall that causes a good bounce on the surface of the water, and a large area of water that is not covered with plants, will most likely provide all the O2 that you need.
As for cleaning up the "tea" - it will clear up on its own as it settles, but you can maybe stuff some extra filtration material into your filter (again, depends on your setup)to hasten the process.
Have fun with your new pond!
Ronaye

Probally peat in the dirt that caused the discoloration. Some very fine filter material such as the polyfill used to make pillows might be useful if you can add it to your filter. One question- are you using regular perrenial hostas for underwater plants? I have not heard of this plant being used this way and don't think they will survive under water.

I too find oxygenators more trouble then they are worth. When I did use them I would tie them to some rocks and sink them down.

If the water really is tea colored and it isn't material floating in the water, based on what you described in your test with the bowl, then filtering the water through some activated carbon will help. I usually put some carbon granules in a mesh bag and leave it under a waterfall source or in a stream with flowing water. The carbon will filter out the tea color and "polish" your water.

Otherwise, if it is particulate floating in the water itself, then the poly fill or other filter material described above will work great.

Good luck!
-Chris

Chris is correct that the Activated Carbon (or Activated Charcoal)will remove the stain and also any odors. You can find it at Aquarium supply stores or at garden centers that carry supplies for African Violets. This is not the charcoal you use for grilling your steaks. An easy way to figure out if you have a particulate problem or a stain or both is to full a glass jar with pond water and let it sit for a couple of hours. Particles will separate out, stain won't, as you have discovered. Hostas are pretty tolerant when it comes to soil. Clay is very good and you are likely using it for other water plants. Peat is notorious for tannic acid stains yet I often see it in potted water plants at nurseries. Another additive that annoys me is Perlite. Avoid using those or be prepared to repot.

The easiest way to clear this up is to drain and start over.

Do not put any potting soil/mulch/peat in the pond. Most pond plants can be grown in pea gravel or old fashioned clay kitty litter. Waterlilies require clay soil to do their best but can survive in gravel or litter if well fertilized.

I've never heard of hostas being used as underwater plants. No idea why anyone would do that. They'll get covered with algae and gunk and you won't be able to see them anyway.

Quilt batting can also help clear the water, if placed in your filter system or skimmer.