saltwater help

I’m not new to aquariums I’ve been keeping fresh water tanks for over 6 years but I am new to salt water. At the moment I only have a 10 gallon salt water with just snails and hermit crabs and a very small pincushion urchin. I’m about to move the fish I have in my 36 gal bow front tank into a 55...

Wondering what this inlet is. I actually was looking for another tank to house a reptile when I came across this tank at a second hand store. Reef tank? Looks like about 40 gallons. Any input is greatly appreciated. Thanks!

So I’ve done a lot of googling, and everything I can find is all about acclimating freshwater mollies to salt, but I can’t find anything about the opposite. I was setting up my saltwater aquarium and wanted some cheap cyclers for my tank, so I decided to go with mollies because I read that...