Auto top-off - aqua safe

[Matt]

This is for my saltwater mixing rig, not my reef, so double-and-triple failsafes aren't so important.

I have an aqua-safe ro/di. It has an auto shutoff valve (a pressure solenoid?). If I tee off that to a routine float valve, is that sufficient?

I'm reluctant to trust either a float valve or the aquasafe auto shutoff, but I've seen people post that technique...

If I put in a solenoid, is a pressure-only or electrical solenoid preferred?