white mangroves like to be a lot dryer than reds or blacks
but it will defiantly be cool. they need a lot of room though im planing on building a out door sump when i move so i can grow red mangroves
scrape some of the purple off the power head to seed the rest of the tank with it, once it starts to grow it will get to the point were you hate it though lol
dont let it get hot and keep it in the dark, make sure you tell the lfs that the fish is gonna be in the bag for a while and they should fill the bag up with extra O2. 24 hours isnt that long of a time in a bag, when they get shipped to the US they are in bags for at least 24 hours. hope that helps
i would try bigger water changes and feed like every other day, and also try changing the filter sock every day instead of every 3 or 4 days because they can become nitrate factories i know that your water is testing zero on them but the cyano is eating all of the nitrates it can get to grow...
that reddish brown thing looks like aptaisa and ive never heard of only adding a few lbs of live rock at a time usually you add it all at once and let it cycle
my water comes out of a salt water well, the cal is around 800 a dkh of 17 and i dont remember the mag (i dont test for it) and i change my water when the cal drops to around 500