Safe to use in an aquarium? The bag doesn't say what's in it.

I just use the play sand that they have.

Out of curiosity I looked at the Quikcrete MSDS for the patio base sand, they only categorize it as "CALCAREOUS OR SILICIOUS AGGREGATES FOR USE IN CONSTRUCTION" in the PDF. Unfortunately that PDF seems to cover all of their sand products.

Under the hazardous materials section they do list limestone in addition to quartz. You could test by some vinegar to see if it bubbles, or HCL, some form of acid.

It's probably safe, but last time I saw a bag it was seriously dirty, lots of rinsing would probably be necessary. I suspect they'd need to list any additives if they were dangerous. Good rinsing should eliminate any soluble items. I'd probably pass though if the purpose was just for something inexpensive. I'd recommend the play sand for certain in that case.

I am on the look out for a sort of larger grain multi shade sand, those various construction grades are probably good for that, whereas play sand tends to be either white or beige.

In addition to the already mentioned sands, pool filter sand also works well.

It's not as sharp grained as some of the other sands, and it usually has some darker/black grains to add a little variation to the color.

Ditto! I would absolutely not use it. Horribly dirty.

The leveling sand is very angular in cut and extremely mixed in particle sizes. I would never use it. Also, play sand is often much too fine and compacts easily.

As already mentioned Pool Filter Sand is a much, much better option for any type of sand product. Anything that's used in a swimming pool needs to not alter your water's chemisty. The particles are a better size and more rounded.

They add a anti-mold/mildew agent to a lot of the leveling sands. Some of the bags will tell you this in small print on the bag.

I went there intending to get the pool filter sand. They had "Pool Filter Sand PLUS" which had some kind of ammonia trapping quality. That concerned me. I also didn't care much for the texture..it wasn't "sand" at all..more like kitty litter.

The Pool Filter Plus is totally different. I went to Lowe's and that's all they had. I believe it was >$20 for a box. I picked up a bag of regular ol' PFS at Home Depot for <$5. It did not have any of the anti-mold agent, as evidenced by the green texture of several of the bags.

I use the PFS in one of my planted tanks (with gravel spread around on top); I have kuhlie loaches and they love to dig in the stuff.