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.
Neptune has designed a Magnetic probe rack that will hold up to 4 probes with one hole being slightly over-sized to hold those larger probes like the Neptune temp probe. By simply placing the MPR in your sump or tank, you can now securely hold all your probes in a single spot. If a probe is left loose their is a good chance it may float with the business end being exposed to the air and causing a false reading. The Neptune MPR can work with glass up to 1/2" thick and keep all your probes secure and safe.
