Yes in summer a tank can be done outside. I myself and friends have had tanks and patio ponds outside with tropical fish.
How much water would you need to water your garden?

i dont need much but i cant have something too big. i think the max would be 50 gallons

Hey Texas

Be carefull of the suns position, I had direct sun on my outside tank for 3 hours and I could not stop the algea from growing. I refered to my outside tank as my above ground pond, enjoy the hobbie however ouside light is a dream for algea.

oh ok. another question. how could i add oxygen to the water? I dont know if my extension cords are able to reach my garden, so are there any other ways?

Yes, it is fun to put containers outside for the summer. Do not worry about a electricity or addint a pump...as long as the tank is very shallow. I recommend large plastic (undrained pots) or shallow plastic storage containers over a glass tank, which may braeak. Add a few small liverbearers (guppies, platies) or white clouds, or other small fish. You will be amazed how much they grow and reproduce over the summer. You don't have to feed them as much either as they will also be getting insects etc. that fly or fall into the water.

ok so i have an idea of what i need to do

*need a plant - anacharis
*need fish - preferably live bearers and/or one goldfish

so would the tub i want need to have depth or width?

I suggest width

why width? im just asking because i thought you would want depth. you know, so the water wont get too hot. but i guess i can only find out if i try.

width cause of surface area,more surface area the better.

oh. ok. so having a longer tub would be more beneficial

You can keep a few fish in a half whiskey barrel along with a few water plants and they will take care of shading it to reduce algae. A feed trough will work as well. I have a small preformed pond that I keep goldfish in and that worked fine. You can get the small preformed ponds off craigslist cheap if you check it fairly often.

You might want to do some reading over on the pond forum. They do little water features, too. They know about weather, heat and sun issues.

Wow its been some time since i have responded! I dont think water will be an issue this year. we have gotten so much rain it is ridiculous!!! my garden is practically flooded.