Are you really suggesting 820gph of flow for a 10g tank along with filling it to the brim with rock further decreasing water volume to 5 - 6 gallons max?
Shoot for 10x - 40x the tank volume per hour in flow. This is the commonly accepted range of flow rate for a salt water aquarium.
Using activated carbon (charcoal) in the aquarium
The number of aquarists here that actively use carbon in their tanks are a tiny tiny minority. It's 100% a good idea to keep on hand but for practical usage; it doesn't really do much for us. Removing odors, clarifying the water, and removing medications are it's primary uses and a healthy tank should have no need for any of that. I would suggest creating a thread asking people if they use activated carbon for feedback on just how commonly used it is.
Boyd Enterprises | Chemipure - Boyd Enterprises
Says it lasts 4 - 6 months on the site and most hobbyists I've heard from agree.
Potentially correct, also extremely vague. Water changes in a reef tank should be done based on how they are needed. A weekly 10% change is the standard but you should also be regularly testing your water to watch for anything wrong in your tank such as rising nitrates and phosphates as well as anything else going out of line. If you see parameters going out of line, then do a larger water change to make up for it.
Your water changes will also vary based on the type of tank.
For example:
FOWLR - These are the most tolerant to increased nitrates and up to 20ppm is well tolerated by the fish.
Softies and LPS - These are well acclimated to more "dirty" water and will handle up to a 10ppm of nitrate quite well.
SPS - These are the least tolerant. You will need to shoot for as close to 0 nitrates as you can get.
With a little reasoning, a sps tank will need a lot more water changes than a FOWLR tank.
I couldn't agree more, which is why I posted links in my response. Never be afraid to ask people where they got their information.