Real Borax? I would think it would just lay there in a pile on the bottom of the tank.
I clean mine at the end of the season by using a wand I made to go down the toity. It's a pvc pipe made out of left over plumbing pieces.
At the bussiness end, there are two 3/16 holes. Lower hole drilled at 90 degrees and the top one pointing slightly upward.
The pressure created by all the water having to go through those two small holes is fantastic - especially at CG's with high pressure to start with. I have my DW watch the panel while I blast the sensors and it gets them perfectly clean. I go on to blast the entire inside of the tank and it gets stuff out that the built in sprayer, geo or soap treatments can't touch. Especially stuff stuck in corners or on the ceiling of the tank.
Scott