Backyard Aquaponics
A place to discuss aquaponics

Hi. Does anyone know if oyster shells will work well in a flood and drain system?
My interests are in finding free lite weight media.
I think walnut shell might be good.
Thanks!

i used them for years in Koi ponds, as a grow media it will work at a pinch but there not very nice to work with, much better as just bio media, especially so in a trickle tower filter.

Only concern would be the affects of the oyster shells on the PH. It should in theory raise it.

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I'm not wild about the oyster shell idea. I think that you could wind up with pH control problems (because they are calcium carbonate), at least that's what I would expect.

Walnut shells would break down over time - some other things I've seen work also have this problem (coco coir for example).

To dasboot - Good to see you back Andreas

Scotty its nice to be back and will be more of a regular here as before, this is were i started and want to continue, i have learnt a lot and only to willing to share back.

Oyster shells as you say are 98% Calcium Carbonate, but they need an acid to dissolve, so they don’t do anything until the PH drops below 6.8,depending on the amount of nitrification and the amount of oyster shells is what happens next. If you had a lot of shells they would try to keep the PH at 6.8, they switch of if the PH goes higher, they cannot go on raising the PH. They are and have been very popular in Koi keeping for many years and if you look at some of the Japanese breeders of high end fish you will still see them in use. For a trickle tower they would at the top of my list as the surface area is massive, again in a bio filter with such a large BSA they are still a good media to choose.

Egg shells work good too, I've used them in the past just microwaving them 30 seconds to kill anything on them first. I didn't do any scientific calcium tests though so don't know if they really did anything but it's free calcium from your breakfast lol.