What kind of clam are we talkin about here? Gigas? Maxima? CLEANER? The reason I ask is because when you mentioned a clam included with a new clean up crew, the first thing I thought of was the regular old eating type clam that some folks toss in their tank as a 'cleaner'. http://www.google.com/imgres?imgurl=http://cn1.kaboodle.com/hi/img/c/0/0/68/5/AAAADOQ1rS0AAAAAAGhVxg.jpg%3Fv%3D1250484422000&imgrefurl=http://www.kaboodle.com/reviews/cleaner-clam-mercenaria-mercenaria&h=199&w=300&sz=19&tbnid=7LQPN8Y3ncy5eM:&tbnh=77&tbnw=116&prev=/images%3Fq%3Dcleaner%2Bclam&zoom=1&q=cleaner+clam&hl=en&usg=__uvhRKXEx-5LU1KYrMtdHzO6ji6g=&sa=X&ei=eMHvTNG5L4O8lQertsy1Dw&sqi=2&ved=0CC4Q9QEwAw
Edit: If that's not what you have, then get it out and good luck.
mythI thought if the clam was over 3" then it wasn't as reliant on phyto and moreso just light and fish waste.