letting rox sit in ro water overnight (in advance) and stirring it a few times will cause almost all of it to sink.

in theory a quick rinse with ro water should be better than tap but there's water contact (and fast moving as well) for like 10 seconds. i highly doubt the carbon becomes used up to any detectable degree but i suppose it's possible.

They sell the Spectrapure dual media reactor, adjustable flow to each reactor, it's what I'd buy if I didn't just run carbon in a bag in the bubble trap of my sump.

I'll try RO style reactor and let carbon soak in RO water 24hrs. Just confirming before sit in the water I still need to rinse it right?

I just rinse (no overnight sitting), and then put it in the cartridge that sits inside the RO canister. I have a sponge at the top of the cartridge (outflow) and it does not plug.

I do have a 3 canister reactor, and the first one is just used for pre-filtering the water. But it does keeps the crap out of the carbon (middle canister) and GFO (3rd one) canisters.

The only maintenance I do is stir up my GFO every 2 or 3 weeks to make it last longer. And that is very simple and quick. Just unscrew the canister, take out the cartridge, shake it around and re-install.