I had a 150 gal tank when I got married like 25 years ago
I forgot more then I remember
Thanks for the advice
How to treat Algae issue??
You said clean tank and new sand..
Does that mean new filters?
What temperature do I need tank to be at before I add everything back to it?
By cleaning the tank, I mean just a good wipe of all surfaces with a sponge and water to remove crud and algae. You can use vinegar or citric acid if there's calcium buildup. Clean all the filter passages, skimmer, heater and other equipment. Make it look new again before you add everything back. That's why an in between holding system like buckets or brute can is helpful.
Replace the sand because historically disturbing a full sand bed and reusing has led to worse water quality problems. It's safer to use new sand.
Whatever filters you have in an all-in-one system would best be initially just rinsed well in tank water (that you are going to discard) and reused for the first month or so. They should have valuable bacteria on them and you want to preserve that while it's settling back in. The live rock will have the majority of useful bacteria on it but every bit helps.
Aim for 77-78 degrees is a good common target. Some people run 80, some run 75. I personally aim for 77.
I see alot of cyanobacteria and some hair algae. Likely has high phosphates. The fact you are going to clean the tank and do a big water change is going to help right off the bat. You can pull or cut the hair algae off the rocks when they are in the buckets. Try not to suck any of that cyano out with the water when you tear the tank down. Once you are setup at home and things are running for a couple of weeks, get a clean up crew (cuc) of snails. Astrea, trochus, cerith, turbo are some popular snail choices. Maybe just start with 4 to 6 total snails - don't want them to starve in case you do too good a job.
There are chemicals for treating cyano but I suggest you avoid that. Let it run and see how it plays out. I've never treated cyano and it just goes away on it's own.
Hopefully the seller is giving you test kits for PH, alkalinity, calcium, magnesium, nitrate, phosphate. If any are expired, get new ones. Avoid API test kits. Reputable test kits are Salifert, Nyos, Aquaforest, Hanna.
Mix your salt to 1.025-1.026 specific gravity. I do 1.025 personally but the ocean is 1.026. A refractometer is best for measuring but I'm guessing you are going to get a plastic swing-arm hydrometer with the stuff. It will do for now.