Not a clam but sorta

using cleaner clams and such to reduce nitrates wont work. they are strict filter feeders that need lots of particulate matter just to live, way more then a typical home aquarium will have. unlike Tridacnid clams that can remove dissolved nutrients (nitrogen/phosphorus) directly from the water. cleaners only remove the particulates. by removing the particulates before they have a chance to break down/rot and turn into N&P they can (on paper) reduce N&P, but just to keep them alive you would need to add lots of particulates, defeating the purpose.