Are TETRA TEC APS 50 quiet pumps, and can they go on a biorb 60l?

Yes and maybe yes. this question was asked recently on Yahoo and while everyone agrees they are quiet, the manufacturers of complete units tend to deliberately make things so that competitors equipment doesn't fit. We unfortunately never heard back from the person who was going to use one in a biorb.You may have to get one see if it fits, and if not wrap it back up in its package and return it.at least from the experience you'll get and idea approximately what fits in biorbs.