Hey Edward interesting indoor system ... just realized it was in your garage, something I am not sure I am allowed to use my garage for.

I was going to ask you how you got the IBC 300gal through your door, I know the container would probably squeeze through but the metal frame would not. But now that you have walled your system in I am assuming you also walled in the metal frame >.br/>
Some questions for you and some suggestions
How much did your system run you, with lights ...

I suspect you will get root growth in your bed drains, but I don't have anything to offer on how you could deal with it outside the obvious. You could try popping off the bottom drain pipe and rotating the grates 360 degrees every one in a while with a two prong fork device, being careful not to snap the plastic grate.

Has your Ph dropped yet in your garage system, if it still hasn't dropped it could be something in your media buffering it. It seems you are using the same media as you did in your barrelponics though so could just be the water, maybe gathering some rainwater would help like it did for your Bponics.

The external bells are really neat, you might be able to extend the outside pipe down with say a T fitting and the bottom could serve as a swirl filter of sorts for your outside system. This way when the bed is not being flooded you can pop off the bottom, remove the solids, and pop it back on.

Since the system is in your garage how do you plan on cooling / heating the grow area. You mentioned it was cold and you had to use a space heater, but what happens when summer comes do you expect to keep the door open so it can receive AC from your central system? We get down to about 22 in the winter and up to 110 in the summer ...

Welcome to the community look forward to updates :D