My bad I see "second hand " crushed coral at end of post 1.
How well did you rinse it?
If not real well then run with Hank and add salt before whatever is in used CC is killed from wrong water.
He did mention you need ammonia anyways to cycle and I noticed you didn't mention your "six week" cycling plan?
You have very little control over such a time line without a good plan.
How are you going to cycle(grow proper bacteria?)
Get a resavior(44 g brute garbage can??) and float valve for that ro
and fill easy!