That's not a ULN system, those use live rock or some filtration medium and usually carbon dosing to rapidly process the nitrates and some phosphates to keep them low. A system the way you described it is a quarantine system with no bacteria load that will perpetually cycle/crash and kill most anything in it after a week or so.
I run low nutrient SPS with only 2 fish (Kole tang and mandarin) using live rock, siporax, vodka dosing and a badass skimmer for filtration. I feed A TON of aminos, reef roids, and other coral food along those lines, so the tank isn't ULN but always has some nitrates and phosphates available for coral food before it's processed. I dose the recommended weekly dosage of Acropower every day. When I ran ULN the growth was ok, but now feeding enough to crash a medium sized tank you can almost chart the daily growth of SPS.