I went out and got a bag of quikrete play sand, a lot of people online are considering this stuff some sort of voodoo due to the fact it's made by a cement company. Fact is, from what I've researched, this stuff is sterilized, and I used to have some in my own back yard in my sand box as a kid. People say that cement sand causes burns over time, and will harm the fish, but this is not cement sand. It's play sand, quikrete is just the company that makes it. As a child, I never got any burns, no rashes, nothing from playing in the sand box and eating the sand. (I was 4, give me a break.) I consider the idea that due to the fact it's produced by a company that sells a lot of concrete products, it's not safe for anything, to be a load of crap. The second thing that people have been saying around the internet is that it's far too fine to be used in aquariums, and it'll just fog up the water non stop. This is the main thing I'll be looking after. I'm usually a user of petco brand sand, it's the only non aragonite based sand I can find around here that is made for aquariums, so why not. The stuff is good, if you were wondering, by the way. It's just a bit of a wallet sink at 17 dollars per 20 pounds. It could cost a load to get enough to fill a large aquarium. Why quikrete play sand, well, it's the only stuff out where I live which is sterilized sand and readily available in major hardware stores. I'm using it in a 20 gallon hexagon, which is currently empty. Aside from a tacky plastic hut which I thought was cool when I first started, some cheap plastic plants, a filter, and a heater. I've already went ahead and rinsed it out. I must say, it's much much much harder to clean than petco's sand. I did a good rinsing for about 40 minutes before I could see the sand itself in the bucket (note, I filled the bucket up 1/4th of the way with the sand, and ran it under a heavy duty utility sink, swooping my hands around on the bottom) I watched it settle for a while, then once again swirling it around, which kicked up even more grime which needed to be rinsed out. The entire process took about an hour. This work alone makes the 17 dollar bags of petco sand seem worth it, along with the fact that you can get it in the color black, which in my opinion looks much better than the dark tan of the play sand. I usually get the whole 20 pound bag of petco sand cleaned and ready within about 10 to 20 minutes. When I felt comfortable in a sense that it wasn't going to break my filter, I went ahead and added it to the aquarium. The filter (which is older than I am, and made by a company that seems to have gone out of business quite some time ago) is still working fine, no crackling, no tell tale signs of the impeller being grinded by the substrate. The filter intake is about 4 inches above the sand. It cannot go any lower. The water, however, does not look at its greatest in the least. It's cloudy, even after all the rinsing, but you can still see the back of the tank. Looking at one of my tanks with crystal clear water, then back at this one, though, it's not a pretty sight. If you make a switch to this sand, be sure you have somewhere else to keep the fish for a while. Perhaps a couple days. I'm unsure of if the cloudiness would harm the fish, but I wouldn't want to take my chances. I added water into the tank from it being mostly drained the same way I always do, putting my hand in front of the flow from the pitcher to disperse it and keep it from messing with the substrate. The substrate as far as the eye could see was not shifted through the process of me adding the water. I'll be updating this tomorrow to tell whether or not the water clears up. I'll also do a 60% water change this evening. EDIT: This evening during the water change, I did a quick siphon over the bottom to pick up any super fine particles that may have been missed during the initial rinse. The tank's water is now crystal clear, and I have to say, the final product is looking good. In fact, I think I may be using the other 40 something pounds of it for my other aquariums, I like the nice natural look of it. Although it's less heavy than petco's sand, I'm not at all worried about it getting sucked through my filter intake. once I find a few more fish to help turn the substrate (although my cichlids seem to do a good job of it themselves) I will be quite pleased with the results. CONCLUSION: Yes, quickrete playsand is safe and cheap option for aquarium usage. It will take a LOT of rinsing, and may or may not fog up the water for a while. From my own personal childhood experience, it is not toxic, and it says on the bag that it has been sterilized, which further disproves the theory that just because it's made by a cement company, it's bad for your own and your fish's health. It is not so fine that it will permanently fog your water and break your filter, just be safe to keep the filter intake a significant distance above the sand, as you would with any fine aquarium substrate.