For that small an amount of water, look for a "fountain pump". As a general rule, sizing a pump for a pond, it is suggested the pump circulate the volume of the pond each hour. When you say, "barely creates bubbles", are you talking about an airstone and aquarium type air pump? If so, many times the air pump may be working, but the stone has become clogged. Try lightly scraping the stone with a sharp edge (like a knife) to remove clogging material or just replace the aeration stone with a new one.