Backyard Aquaponics
A place to discuss aquaponics

OK...I'm going to build a new system. 4' by 8' by 10" deep. Using hydroton clay pebbles for grow media. I have figured the weight of the clay pebbles at 418 lbs at 10 bags. Does anyone know how many gallons of water it would take to fill the grow bed to 1" under the surface of the pebbles (or 9" deep)? Not sure how to figure the hydroton displacement. I need to know this due to different construction of the wood frame to make sure it will support the total weight. Don't want it to come crashing down and smash my Tilapia into flounder. Thanks....

If you can use one of the conversion programs or web sites to figure out the gallon amount that the grow bed in total holds and then figure that 50% of that space will be filled with water. If you want more safety factor, call it 60%. Then figure out the weight for that amount of water. I believe most of us figure that it takes about 40% of a grow beds total volume worth of water to flood the grow bed but that number is only an estimate which is why I said use the 50% number and up it if you want more safety factor.

I did some crude experiments a while back to calculate the water and media percentages... With the media wa found that on average the water took up 40% of the capacity of the relitive GB... depending on the media it varied only by 2% or 3%... however, we never tried with the clay balls (too expensive)...

I think we worked out at one stage that our beds filled with 500L of expanded clay took about 180-200L of water to fill it to about an inch below the surface.

Thanks Earth and Aquamad...40% seems to be the agreed upon communal ratio.