Solar Pond Air Pump
You can easily run air to any outdoor pond or tub with this cheap combination of tools. A USB powered air pump run by a small solar panel with USB outputs is all you need! The video below shows my setup running on my 100 gallon guppy tub - which you can read about here.
Setting up Solar Powered Pond Aeration
These little USB air pumps can drive a steady stream of air to the bottom of a 2.5 foot deep, 100 gallon stock tank.
Such small air pumps use very little power, so a single solar panel hung in a sunny spot can run one for most of the day. While this setup won't provide aeration at night, it will increase air exchange during the hottest part of the day. This helps prevent the tub from becoming stagnant and keep the water oxygenated for the fish.
Look for a cheap 20 watt solar panel - like the one shown below - that has USB ports as its power output. Then you just have to plug the air pump into the panel, and place it in a sunny spot. I hung my solar panel on the side of shed, and it powers the solar pond air pump for 10-12 hours a day during the summer.
Start backyard tubbing with your own 100 gallon stock tank! These are great for small outdoor ponds. The rubbermaid construction will last for decades, and they are much cheaper than a similar size aquarium.