The amound of LR(1.5-2lb per gal) that is often suggested is way too much IMO/IME.In my 75,I use roughly 65lbs of LR.Its not the weight of the LR that should be considered,its the shape/density/porousity of the LR that is important.I recommend useing enough LR to fill 1/3 the tanks volume.
Obviously,Mandarin fish feed on copepods and that is why you probably feel like you need alot of LR.It doesn't really matter if you have 40lbs or 100lbs of LR.The population levels of infauna in a reef tank(pods,worms,etc..) are in direct proportion to the amount of food/nutrient import the system receives(not by how much LR is in the tank).The degree/level of predation in the display tank will also play a role
in a tanks infauna population.So,if you want to grow pods,feed your tank daily.When i say feed your tank,I mean the fauna/corals.The fish should be fed daily as well IMO.