I am planning for a 1ft grow bed and to fill with rock gravels.
In order to reduce weight, in the middle level, I propose to fill with Bio-Char (Char Coal)
small lumps mingled with coal in powder form. This is available in plenty in my area
and quiet cheap.
Is this a good idea? and will it properly filter the fine particles of fish waste?
The question is not easily answered. If your char is powdered - no do not use. If your char has plenty of form and can support the colonization of micro=organisms yes.
I am using lots of lava rock for the same reason and am experimenting with Biochar.
The Char can work but you much make sure there is some structural integrity left.
Newbie here wondering the same thing. Though you say "small clumps mingled with coal", do you really mean "Coal" or Charcoal? Charcoal is extremely porous, and I think it would be great as part of the growing media in a grow bed, as it is in a conventional garden plot. However how much to use? I think a layer at the bottom would be good as the final filter in the system, just as there is char incorporated into many aquarium filters. I use the char out of my filters in potted plants, and soak the used filters to get home made organic fertilizer for the potted plants and to apply to the vegetable garden.
I know that is one step behind aquaponics, but right not I don't have my grow beds set up, our first Tilapia fry are about to hatch, momma fish is in a tank awaiting the delivery, so excited after getting the Tilapia last year and growing them to maturity in a 55 gallon tank in my living room, the delivery tank is on my kitchen counter so I shouldn't miss the event!
@susan. new to this myself too, but like you have gardened and raised fish for along time.........just not in the same system :/.....your thoughts on the charcoal was what I was thinking too, but again im new to this so ............
side note I have also used skimmers in my aquariums (does a much better job then filters at removing waste) and used the consentrate in the discard cup on houseplants and in the garden.......results are WOW lol.......and is what lead me to look into aquaponics