NO! Dont let tap water any where near your marine tank! This would be better:Does this plan sound okay?
I put my rinsed sand in the tank (Not live, will add some live later). Fill it up with tap water. Let the chlorine remove itself from the water. Add salt. (Powerheads will mix it). About a week later start to add live rock and sand.
For water changes, I will use a bucket, powerhead, and heater to mix my salt water.
1. Add all equipment needed
2. Add RO water to tank switch on all equipment and let it run for a day to make sure it's all working correctly
3. Make sure tank is up to correct temp (around 25 degrees) and add salt to correct salinity, let this run for around 24/48 hours
4. Add live rock(cured) to tank (around 1.5kg per gallon) allow to run for a couple of days checking ammonia/nitrite
5. Add sand (doesn't need to be live as the live rock will seed it)
6. Continue to monitor ammonia/nitrite till they spike and drop to 0 then check your nitrates(by this point you will notice a build up of brown diatom algae)
7. Do around a 30-40% water change to lower nitrates, let stabalize for a day or so then add your clean up crew members to help reduce the diatoms
Dont add the same type of sand you would use for your cichlid tanks, make sure its a marine aragonite based sand