Almost ready to add water - advise please!

[monocus]

you are ,but you will still have a small sand storm which will leave your water cloudy for a few days.if you can,rinse your sand before using(waste a pail of r/o)

[Enigma]

An easy way to avoid a huge sandstorm from pouring water into the tank with sand in it, is to place a plate or a bowl on the sand. Pour the water onto the plate or into the bowl.