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I have split your post from the other thread to give you more specific answers about your set up.
Originally Posted by SRepking
I have read in this thread
that with LR
and Detritus eating inverts, that mechanical and biologial is not nessecary
The biological filtration is provided by the sand and rock itself. If you wish to rely moreso on natural filtration, I would almost double the amount of the LR
or add 100ish lbs of dead base rock to alleiviate some of the cost. The sandbed can be anywhere from 1-2" and if using a proper oolitic aragonite sand will still get a decent amount of nitrification from the sand. The rock will be the primary form of filtration as the anoxic area's within will convert the nitrates to a less harmful nitrogen.
is not really needed at all providing the natural sources are in sufficient quantity. You may still want to opt for a sump over the W/D as it will add to the total water volume, provide a space for unsightly equipment (skimmer, heater and such) and reduce the need for intank PH
's depending on the velocity of the return pump.
is also not something that you would call neccessary but can be a benifit from time to time. For items in this category, it will moreso depend on the stock level of the tank.
You will find the use of a protein skimmer or macro algae planted refugium
much more beneficial as an add on to the natural filtration in the tank.