We had a rockpool tank set up for a couple of years. Most interesting tank we ever had but keeping it cool was a major problem. They could take higher temps for short periods of time but a room sitting at 28 deg wasn't good. The water needs to be 10 - 15 degs.
We had a 3ft tank, added sand and rocks from the beach and caught all sorts of critters in the rockpools - triplefins, rockfish, shrimps, anemones, sea urchins, chitons, hermit crabs etc. Never fed them either, just topped up the water with sea water every now and then. We used sea water as we figured it would have the microscopic greeblies the others fed on. Must have worked as everything survived. We also added sea lettuce regularly. Lots more critters would come with it too
We had a couple of small paua at one stage but they do not cope with higher temps. An octopus was doing well but was an escape artist who discovered he could not overcome carpet fluff!
We didn't light the aquarium as there was nothing in it that required light. The only plants being the sea lettuce which was eaten by the inhabitants.