Requesting FEEDBACK on Feedback on my custom sump design

[zeroinverse]

Here's my SUMP/REFUGIUM design

OVERVIEW
45 gallon tank to be split to create a refugium display and comprehensive sump filtering

1. overflow drain (A)
2. refugium spanning entire front face of sump (C1)
3. algal turf scrubber (B1)
4. macroalgae tumbler (B2)
5. protein skimmer chamber (B3)
6. remote deep sand bed (B4)
7. pump return chamber (D)

A - Overflow drain is split to high-flow (B1) algal scrubber & slow-flow (C1) refugium

B1 - vertical algal scrubber output controlled flow to macroalgae tumbler (B2)
B2 - macroalgae tumbler output to protein skimmer (B3)
B3 - protein skimmer high-flow output flows across RDSB remote deep sandbed (B4)
B4 - RDSB high flow prevents detritus accumulation and outflows to sump return chamber (D)

C1 - refugium slowly overflows into sump return chamber (D)

D - sump return chamber flows back to main display tank


Suggestions on
1) how much "flow" I should design for a 90 gallon display tank and 45 gallon sump?
2) how much "flow" through refugium?
3) will the protein skimmer flow over the RDSB be sufficient?
4) Thinking of using "Special Kitty" cat litter as a mud RDSB to help enhance nitrate conversion (i.e. denitrification) - due to more ability to get anaerobic/anoxic regions.
Thou

[zeroinverse]

bump, anyone with feedback?