This acrylic bracket is designed to hang up to three heaters in the sump, preferably between the baffles where they are fully submerged at all times, and water has to flow over them to the next zone.

The bracket is made with 3/8" thick acrylic, with a 1/2" diameter handle.  It's designed to sit in 8-9" of water. The heaters are loaded into the acrylic and lowered into place carefully. You will need to make sure the length of the heaters won't be a factor, and be aware of the cords so everything tucks in nicely and stays positioned properly. Ideally once installed, you won't have to touch it until you need to do deep cleaning in the sump.

This bracket needs 2" of space to fit.

Dimensions:
12" wide x 1.75" deep x 10" tall
Holds up to three 1" diameter heaters

The heaters will not melt the acrylic. I've included some pictures of my own setup that has been in place since March 2020, and the heaters come on twice a day, daily.  And I'm using 300w heaters.