I used about 450 lbs of it in my 300, just MAKE SURE you rinse it first...even after the rinse expect it to be cloudy. I found that filling a pillow case or something with sand then rinsing it with a hose works very well. Good call with using it though, cheap and good looking. ( I also have friends who have successfully used it as well)
Don't buy the expensive "kid=safe" type, The reason it costs so much is it is treated with fungicides. The only place that I have seen it was at Bigtoys in Tacoma and it came in 100lb sacks. I don't like builders sand either because it is to abrasive.