I myself have used OpenSprinkler to control LED lights directly. As long as the device you are switching meets the voltage output of OpenSprinkler (on DC-powered OpenSprinkler it’s basically the voltage of the power adapter, so roughly 12V if you use 12VDC power adapter), and current per zone (up to 2amp per zone on DC controller), it should work fine. Your fished feeder should work well with DC-powered OpenSprinkler, with a 12VDC power supply.