Those limpets will not help with algae control, as was said they rarely move. I have a bunch of ther local periwinkle snails in a tank for two years now and the temp in there now is 85 degrees. I sometimes throw a handful of them in my reef but the hermit crabs kill them. If you don't have hermit crabs they will live a few years. I can collect about 1000 of them in five minutes. I will be going out in an hour in my boat to a tidepool in Port Washington to do a little collecting. There are thousands of baby horseshoe crabs but I don't collect those. I just take shrimp, crabs, worms and amphipods. I will also take a few tiny fish and seaweed as food. Of course there are a bunch of people coming too and we will have a bunch of boats tying up with us so the main theme is partying.
Have a great day.
Paul