Raechal
Fish Gatherer
I bought 4 40lb bags of playsand from walmart in the garden section. They were only $1.67 a bag, which is WAY cheaper than buying a 40lb bag of gravel. 
It wasn't that hard to clean out the gravel, it just took awhile. I wanted to make sure it was as clean as I could get it. I didn't want to fill my 120 gallon with sand and then add the water and figure out that the sand wasn't clean enough and have to empty my 120 gallon by hand. 
So I spent many hours cleaning the sand. I put some into large bowls, ran the hose over it and then stirred it around with my hands. Then I drained all of the water out and repeated that about 4-5 times each bowl.
It wasn't that hard to clean out the gravel, it just took awhile. I wanted to make sure it was as clean as I could get it. I didn't want to fill my 120 gallon with sand and then add the water and figure out that the sand wasn't clean enough and have to empty my 120 gallon by hand. So I spent many hours cleaning the sand. I put some into large bowls, ran the hose over it and then stirred it around with my hands. Then I drained all of the water out and repeated that about 4-5 times each bowl. 
