glass covers are best, but its unfortunate if you cant find a good glass/mirror shop around you. they can do it for you. anyone who cuts glass to spec and dimensions should be able to do it for you.
You need to be checking your salinity each day or every other day. you do not want it fluctuating more than 0.001. And the goal is to have it around 1.025 so you're ok. You will need to top off eventually. its nicer if its a few days as opposed to needing to top off every day or even worse several times a day. A good way to know if you need to top off, is to measure your salinity, see if its at 1.025 then mark your water level. whenever it gets below that level, add FW up to level and you're good.
Watch out for temperature changes. what temps do you keep your tank around? make sure its stable too.
Feed the shrimp every other day once they start to take food. I wouldn't feed on the same day you introduced them though. they probably wouldn't even want anything.
Keep your hands out of the tank so that 1. you don't get stung by the worms, 2. you don't get stung by any coral, 3. you don't get any chemicals on your skin and then accidentally injest them later or rub your eyes, etc. its easy to get irritated with certain things that come from reef tanks. some corals are toxic, so you do need to take care. also if you have any cuts on your hand, you don't want anything odd affecting you.
In FW the worst that could happen is you get some random parasite (mostly from snails) that most likely wouldn't even affect you, but in SW, not only is there still the risk of parasites, but now you have to deal with coral chemicals. I am not even joking. just use common sense and be cautious. you do not have to be paranoid lmao. This hobby is pretty safe unless you go rubbing palythoa corals on cuts in your hand or something reckless like that xD.