redearslider.com

Right now my newly found red eared slider is staying in my large garden, it can't go out, and theres a small pond, with no fish, will it be able to feed itself or not?

It may eat what is in your garden and any bugs that may land in the water. If you want too take care of the RES you could throw a few pellets in every day, but if it is wild which it may not be it may be fine or it could starve to death if it cant figure out what to eat.

I'd give it pellets. Diet in the wild is sort of unreliable. Depending on what's available, it may not be nuitritionally balanced or in sufficient quantities. An ideal diet would consist of things found naturally in a wild turtle's habitat but in perfect balance and quantity - which may not happen naturally.

If the RES you found is wild, he probably could have survived just fine in the area he was originally (or move on if he couldn't). But, you've got him restricted to one area and he's essentially a captive and is dependent on whatever he finds (which doesn't sound like much from what you wrote).

Are you planning on keeping the RES as a pet? If so, then I'd start putting some food in the pond (they only eat in water), add some aquatic plants for cover (and eating) and perhaps add a few feeder fish. If he's wild, he may not be interested in pellets at first, but you can try.

How big is the RES?

How big is the pond (gallons)? Would he be staying outside all year round?