Neptune Systems designed the MPR – Magnetic Probe Rack specifically for the Apex. It will hold the larger diameter temperature probe, pH probe, ORP probe, and salinity probe.
Made from acrylic and with strong neodymium magnets
Works securely on sumps and aquariums up to 1/2″ thick
Dimensions – 4″ long by 2.5″ deep with the screws all the way backed out.