I've only used APC in my other life, in IT using UPS's as computer backups. Really their primary use is to clean up the power/regulate voltage to keep the gremlin type things from happening.
Getting sustainable run time out of a battery backup system is not very economical. Basic UPS systems are measured in minutes and hours, not days. Thousands of dollars to get a modest pump to run bast 12 hours. If it's just a power head or alike for in tank circulation, doable. Sump pumps/heaters/lights no change on a UPS.
Think small gas generator. For UPS's it all about watt drawn and battery capacity.
Apex allows for 2x power sources I was told, e.g. 2 different circuits on different breakers to redundant. With a UPS/battery backup you'd just front end the whole mess I image.
