How Do I Fill Up A 75 Gallon Saltwater Tank?

Planning my 75 gallon saltwater tank and I come across one problem:

How the heck do I fill it up?

I heard tap water can be dangerous, so that idea is already gone.

I thought I could just get saltwater from Petco, but I'll need 15 of those 5-gallon boxes to satisfy my tank!

My only other option is to go non-stop to my LFS to get saltwater.

Another option is to get a R/O filter, but that can cost A LOT!

How do you guys fill it up?

 

Haha, you made me think, I honestly can't remember how I did mine.
I'm pretty sure I had my RODI unit going for a few days to fill it with RODI first, then added salt. I had calculated roughly how much salt I'd need to add, and added in a little bit less than the calculation, waited 24 hours for temp to come up, and for the salt to mix in. Then tested, and added a bit more till I got to my desired salinty.

I was filling bucket after bucket of RODI, then carried it inside and put it in the tank.

It's a long and laborious task the first fill, I think it probably took me about 3 days to fill. I think it's the first lesson in patience when it comes to Saltwater

Another option is to contact your local marine society/club, and see if they can deliver the volume of Saltwater you need. It might cost more, but it's a lot faster. Or even ask your LFS if they can deliver, most will have IBC's (Intermediate Bulk Container)

Oh, and some will say not to add sand first, others say to add it in first. For me, I simply filled with water and got the system running and up to temp. Then added live rock (you need to drain a bit of water to allow for the space the rock takes up), then added sand (after live rock). My idea was that sand will help to stabilise the rock once in position (like the way you add the fence post, then the concrete around it). There's no right or wrong, but just have a think about how you'll add your rock and sand.

 

I bought cases of distilled water from Walmart to set up my tank before I had RO/DI .

 

I filled mine up with bought saltwater. I had three jugs. FIVE trips to the LFS for water. $5 a jug. You might as well go on and buy the RODI filter for $30 more. I figured out the first year I kept my saltwater tank I spend something like $700 on premixed saltwater from the store. So dumb.

 

A cheap RODI system runs $60 shipped from Amazon and it can produce $60 gallons per day. Going to the LFS to start up can be quicker but it is likely to cost you a fair bit. My situation is different than most, so I still get my RODI water from my LFS. It is a whopping .7 miles down the street from my house and RODI is free and RODI/Salt Pre-mix is 75 cents a gallon. They also drop the price to 50 cents a gallon when you are starting up a new tank so the convenience factor made it worth it for me. Unless your LFS charges a ridiculous amount it should still be a better option than running distilled. I would say in the long run though you are best off with an RODI system: