My next step for all of the systems was to create some type of substrate. Well if you read the previous section on installing the grow tanks you will see I mentioned using deep sand beds. On my first farm set up, which was a series of grow out systems off a main tank I utilized DSB’s and think it’s a terrific way to control nutrients and feed the fish and coral population at the same time.
Starting this project in 2002 afforded me the privilege (and luck) of being able to use South Down Play Sand for the Deep Sands Beds paying two to three bucks a bag in comparison to the sixteen I would shell out for twenty pounds back in the late ninety’s, this is one step that saved me a lot of money. Currently I have four of my six tanks set up, and three of those have deep sand beds. The three tanks set up are each 110 gallons. Each tank used about three hundred pounds of the Caribbean Sand to get a height of about five and a half inches in the tank.
One area of concern while laying these beds was what kind of current could I get in twenty inch high tanks, with a six inch sand bed. The answer from my experience was not that much if I wanted to keep the sand bed intact. One area I want to advance dramatically in these systems is the water current. I know down the road I may be removing the sand substrate from one or more of these systems, but not knowing what hardware I would need in the future made this the best way to proceed.
In addition to all of the bags of Southdown I purchased from the local Home Depot, I had a ton of this stuff already available. A portion of it was live and being used in both a 120 gallon tank and 120 gallon sump. I also had more in my garage in garbage cans from the grow systems I had ripped down. In each tank I mixed the bed with new sand on the bottom, a thin layer of live sand from the operating tank, a thin layer of dead sand from my garage and another layer of live sand from the tank. Over the years many people have asked me what method I use to add the sand to my tanks. I was mostly concerned with the milky water from a fresh mix.
I have two suggestions; the first is do not attempt to rinse the sand with water. I don’t believe this step is of any value. For starters you will end up rinsing a lot of the product down the drain, most of which would settle out in your tank. Secondly, the sterilization method used with this sand is baking, and to rinse it through tap water is just having it absorb all of the water.