Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
"Beach Sand" may have some salt content, but salt is water soluble. A good rinsing in as warm water as you can arrange will dissolve the salt, no problem. Even if you went right to the beach and scooped up sand from the ocean the salt and minerals is not the issue (just lots of rinsing... )
However, the other issue is very important.
Most sand IS silica based. If it is NOT silica, then it is something else. Perhaps limestone, or other material that dissolves in water slowly, but can alter the pH, GH, KH and TDS of the water. Yes, test it. Get a sample and put it in some tap water (or whatever source you are using for the tank).
Test the water when you start, and every few days. Test GH, KH, pH and TDS.
If the sand is from a limestone or coral parent material or any other material that will add minerals to the water then some or all these levels will go up. This suggests that this sand might not be good in your tank.
It might work if...
Coral and limestone based materials can help if the water is too low in minerals, and you want to keep hard water fish and plants. I use Coral sand in my hard water tanks. I also prepare the water for water changes by adding minerals so there is not a shock to the fish when I do a water change. Then the coral sand is acting more to stabilize conditions between water changes.