Going from memory so this may not be 100% correct. When I ran ESL some devices would say mobius ready or compatible (can't remember exactly). Those could be upgraded to mobius via ESL with no hardware replacement needed. If they didn't say they were mobius ready the RF module needed to be upgraded. The old module is green and the new one is black. There may be some older devices not upgradable but I'm not sure. Basically if you upgrade to mobius you then can and have to use the mobius app on your phone or other device. Those devices you upgraded can be downgraded back to use ESL. Newer devices are mobius only per ecotech support. I have mixed feeling about mobius. The app randomly changes date and time. Pretty annoying waking up at 3 am with the lights blasting because the app thinks its noon. This doesn't happen a lot but it's often enough that I no longer run radions and only use mobius for vortechs. To my knowledge this has been an ongoing issue and has never been addressed. Also another setback is that mobius is bluetooth only not wifi so you have to be within range to make changes. My other lighting apps are the same so not really a negative but no more changing settings when I'm away. There are also settings that just plain do not work on android. I can not remove a tank which has to be done before a device can be moved to another tank. It does work on ios but if I didn't have an old iphone laying around I wouldn't have figured that out and I probably would have scrapped all of my ecotech gear. The only reason I even bothered with mobius is because I had 7 vortechs and needed to add a couple new ones and they are only mobius compatible. Sorry for being so negative but for the price they charge for thier products the app should work at least as well as the other lighting apps I use. I also use the my Ai app, reefbreeders nexus, and noopsyche k7 app.
