For what it is worth, I have never been a fan of deep sandbeds and have zero nitrates (or at most 5), despite extremely heavy feeding and very messy eaters. I have a FOWLR with triggers, a large wrasse, etc. which is fairly heavily stocked and have no clean up crew. My sandbed is about 1 inch to 3/4 of inch deep in the display of arganite gravel. My refugium has no sand whatsoever and is loaded up with rock and topped off with macro chateo algae. I feed massive amounts of food several times per day (large meaty foods which often break apart into many little pieces which get sucked through the system) which mostly gets eaten, but it is not unusual for some significant amount of food to not get eaten when I feed a bit too heavy. I am amazed by the fact that unlike my prior system and without a clean up crew, I have no algae to speak of and near zero nitrates (usually undetectable or at most 5 when my feeding gets a bit out of control), despite my heavy bioload and feeding regime. My system is about 1 year old. My prior system had about a 3-4 inch sandbed and regularly suffered from excessive nitrate and algae problems. I do water changes at most every three months simply to replace trace elements and usually only change about 20% of the water. My skimmer is also not the greatest and is an air driven venturi type which is rated to handle up to (but not exceeding) my system size. By no means anything scientific, but just my personal experience.
