Backyard Aquaponics
A place to discuss aquaponics

My question is:

What amount of volume will expanded clay take up in a grow bed?


My reason for asking this question:

I am looking at setting up a 500L fish tank + 500L grow bed system using the flood and drain using a bell siphon and expanded clay media.

It has occurred to me that since both the fish tank and grow bed are the same size, in theory (with no media in the grow bed) ALL the water could flood into the grow bed before the siphon starts and leave the fishes with nothing.

Obviously there will be media but how much volume will the expanded clay take up in the grow bed, and therefore how much water will be left in the fish tank for the fishes?

60%, so you will only be taking out 40% max of the water in the FT at any one time.

Gurus correct me if I am wrong please, only in head experience, don't own a system yet.

Do it and see.
After the initial saturation of media you will probably only be filling the pore spaces. However of the 500litres of media the water is only up to a couple of cm below the surface, not the whole volume. I have been quite surprised at how little the water level drops from a 1000 litre fishtank. Not having done what you are asking I cannot give a difinative answer. A solution to such a fluctuation would be to run the system constantly flooded.

I would estimate the growbed would take about 150L of water when flooded. I may be a little bit out though.

You will lose some water from evaporation and i think you''d be needing to top the tank up quite oftan to keep the maximum level of water possible though. I would probably choose a bigger fish tank or run constantly flooded.

2/3 media and 1/3 water, as others have said get a bigger fish tank or run it constant flood especially in the heat we are experiencing in the summer months.

And don't forget that because the water is flooding lower than the top of the gravel there's not as much water.