You can plug in whatever the unit can handle in terms of load. Air pumps should not be a problem at all. They are backup batteries you normally run your computer off of in case of a power outage. The price depends on how large of a UPS you get. First figure out what size you want to get by figuring out what you want to run off of it and for how long. They have free online calculators to help you out. APC which is a major manufacturer of these battery units has one of the calculators on their site. Then check Amazon, Bestbuy, Costco, Ebay for prices.