My friend has it on his 65g. I'm not sure how well it would handle a heavily stocked tank but it works ok on his. Its a pretty good skimmer as Aqua-C makes good products, but it can't compare to other brands like Euro-Reef, ASM, or even the other Aqua-C skimmers. If you aren't planning on SPS then it probably would do the job.
assumming you have a sump there are better skimmers out there for more money. the i use a aqau c remora, and ev180 and love them both for their simplicity. the urchin is just a in sump remora and work just as well. upgrade the pump one size and rock and roll.
I have an urchin skimmer on my 65g currently with no corals. This skimmer works fine right now but I am not sure how it would handle a heavily stocked tank. For a heavily stocked tank I would recommend the Aqua C Urchin Pro or an Aqua C EV skimmer.