Hi Dan, just a question on the pot scrubbers. I'm guessing that you will be keeping your discus in a low PH setup, say around 5.5 to 6.0 PH? I have heard of the potential fir acidic water to break down the plastic over time and releasing "stuff" into the water that could potentially harm your discus.
Personally I would have gone for the large bio balls, (also plastic) but tank safe. A bit more expensive, but worth it for peace of mind. Either that or a mix of Alpha Grog and or Siporax.
Plus 1 for the comment on the leaky bits. Change them out, it ain't worth the risk.
Good luck.