DIY river bottom

today i decided to try and create a river bottom. Success! This is how im doing it....so far, it looks very realistic, its gonna look good in my tank....after it is completed, i may create a background to go with it....
What you need:
2 inch think slab of styrofoam, get whatever size youll need and measure and cut it to fit your tank...
1 50lb bag of quikrete concrete mix, about $7...
I used a flathead screwdriver to carve out the styrofoam surface, making it look like a mud river bottom, i found a scratching motion worked best....
Mix up your concrete mix and make it thin, grab a paint brush and paint the stryofoam with the watery concrete mix....i took rocks, some driftwood, stones, and fake plants and cemented them to the stryofoam and each other...let it dry and be cautious when putting it in your tank....i hear you need to cycle it in the water and do 2-3 water changes over the next 4-6 days,w/o your fish in the tank.....i dont have any pics yet, but it will be done by the end of the week.....