I hadn't heard that about the live rock, thanks.
The fuge I planned in the sump would get its water from the DT, then that would be pumped or overflow back in to the return area of the sump. From what you said, uncle, should there be another drain pipe going directly to the fuge instead of being tee'd off from one of the two drain pipes? I plan on using the BeanAnimal/c2c overflow. Not sure if you can tell from my design, but other than residing in the sump, the fuge is separate from it (the acrylic divider will go to about 1-2" from top).
The sand bed will be at least 6" in the fuge with chaeto and possibly caulerpa.
Do not feed the "fuge" section from the drain line. It messes with the operation of the drain system, and assists in turning the 'fuge' into a garbage dump. If doing a fuge, feed the fuge from a tee in the return line.
The BA system, has only 1 drain line (the siphon) with appreciable flow. This line needs to drop directly into the skimmer section, which should be the first section of the sump. The open channel has very little flow (when adjusted properly) and needs to drop into the skimmer section as well (same water level) due to the interaction between the siphon and open channel. Again, do not split the drain lines to feed other accessories.
An RDSB should have no other life in it other than bacteria. DSBs are simple to implement, however they are very STRICT methods, and straying from the strict implementation, is why they get a bad wrap: They go bad. Most contemporary hobbyists have never used one.
Most comtemporary hobbyists, have a deep ingrained belief that live rock provides some "miracle" filtrationthat you can't get enough of. Although, in times long past, this was somewhat true. The rich bio-diversity on and in Live Rock of the past was 1/2 of the backbone from which reefing was born, back in the late 1960s. The other half was real live sand. (not the garbage that comes in a bag.)
Legislation and curing, have eliminated this Live Rock from the market. To be honest, even cultured live rock does not compare, but it is a better bet, than what you can pick up from an LFS or mail order, that will be nothing but a rock that was collected from the ocean, has some bacteria on it (but every surface has that (bacteria are ubiquitous,) maybe an occasional hitchiker that does no good at all and maybe some coralline spores. This rock will never become "live" in the true definition in a closed system; rather provides material for an aquascape, something you can stick coral too, and a surface area for nitrifying bacteria. Other thoughts on what 'live rock' is going to do, has no basis in science.
Most rules of thumbs for how much rock per gallon, overload the system with rock, for no good reason (other than to seperate you from your money,) and interferes with good circulation. Tanks with half that much rock in them, have no problems producing nitrates at all, so there is no point to adding more in the sump. Pods grow in the main tank (if the system is capable of that,) so there is no point to culturing them. If you need to culture food, try phytoplankton, simple, inexpensive and seperate from the main system.
The argument for in sump bio-diverse 'refugiums," complete with sand, rock (bio-balls,) pods, crabs snails ad infinitum, is a relative of the circular argument. On the one hand, the sump is to remove unwanted material from the system, on the other hand folks want to load it up with stuff that adds to the problem. It isn't very logical.
These are very involved and complex topics.
