Worms pretty much take care of themselves in aquaponics but i understand your hesitation. There is a system that may work for you, it's call a CHIFT PIST system. Aquaponics people are big into abbreviations, Constant Height In Fish Tank, Pump In Sump Tank. Basically a pump in the sump pumps water to the fish tank, an overflow from the tank goes to your grow beds which can either be constant flood or fill and drain as in the case of mine. This water then returns to the sump. This allows you to have your grow beds at a low level than the tank and makes it easier for some to create grow space. In outdoor systems worms happen on their own frequently. the biggest benefit of the worms is waste breakdown for aquariasts.. for people more interested in plant growth they provide inumerable benefits to plants including chelated iron. there is no real need for worms, they are just beneficial.