Backyard Aquaponics
A place to discuss aquaponics

I was wondering about using shells as a growing media. Has anyone done this? At the moment I've got coco husks, which gave me a really low PH. To balance this I added crushed shells, which bought the PH to 7.

So I was thinking about having a mix of shells (broken or whole) and coco husks. Besides balancing the PH, drainage would also be improved. Shells at the bottom of the grow beds would be good as the coco husks may tend to rot if continually in water.

Similar to coco husks, shells are a sustainable bi-product, which makes them very fitting with aquaponics.

Any thoughts?

Sounds a fair idea Plachon.... you're going to have to buffer pH against the coco-husks anyway... as you've found...

After struggling with the low PH, I ended up getting a few kilos of crushed shells from the aquarium shop and the PH was fine in 2 days. I've now got a modified NFT system with large diameter bamboo and crushed shells. Now I'm trying to figure out a source for the shells, because they aquarium shop is too expensive.

Plachon, the local produce store sells 25kg bags of shellgrit for chooks - much cheaper

also TCLynx uses crushed shells in one (or more) of her GBs - no pH probs at all

I'm living in Bangkok, Thailand and can't find it here in the city, however I know it's available in rural areas, plenty of chooks over here!

What does the shellgrit look like? I'm guessing it's quite fine. My idea was to use shells or large pieces of shell in the media. The benifits of mixing this with the coco coir would be:
- enhanced drainage
- PH balance
- Both media are sustainable bi-products and should be available cheaply.

Ah! was gonna ask if you were in Oz

Shellgrit is just sea shells that are smashed up, they do have a fine, medium and coarse ratings - only point I would like to make is that it would be sharp and so be careful when planting in it

This would need to be taken into consideration. I wonder how long it would take to wear smooth from the running water? Besides the risk on your hands, it could also cut through roots.

Any sharp edges blunten very quickly.

Plachon

Try a seafood (shellfiish) processing factory. (You may even get some for free!)

Then find out where you could get someone to pass it through a crusher.

I think that in BKK this wouldn't be a problem.

WHOA!!!!

I wouldn't say no pH problems with my shells!!!!! Just the opposite pH problem My pH is at 7.6 or above and there is no changing it since the shells are mixed with the river rock throughout my system.

Even in the little barrel system where I have one small bed of shells, one half barrel of river rock and one half barrel of wood chips, the pH is still always between 7.6 and 8. I thought that perhaps the wood chips might bring the pH down but it seems that the shells self regulate at 7.6.

Yes use shells and/0r shell grit to balance your pH but I strongly advise against mixing them through out your system since a pH of 7.6 makes iron deficiency a constant issue.

If I had to do it all again. I would not mix the shells with the other media. I would place it in the system as needed to try and maintain a system pH of 7.0-7.4.

Having a pH that hangs out close to 7.5 kinda sucks since to really check it most of the time you have to run both pH tests too.

Ya know, Steve warned me back when I was looking at media. I decided to take one for the team and get the shells with the river rock. This is why I'm sharing my pH issues!!!!
Tomatoes and lettuce don't seem to have any trouble with the higher pH but cucumbers, melons, squash, okra, etc, hate it.

I disagree that a ph of 7.6 is your issue TCL.

I have a PH of 7.6 since day one - shells mixed through the beds.

No iron deficiencies or any others from what I can see.

Agree with the having to run 2 tests though

I definitely have Iron deficiency problems. I don't think our bore water has much Iron in it and chleated Iron is not available from most garden centers around here. I finally managed to get some so perhaps it won't me such an issue. Before I was needing to do foliar spraying with the Iron Sulfate in order to keep some plants happy but that is a pain since it stains everything.

I am keen to know your results - iron uptake at 7.6 seems to be fine. I have a lot of sand in my growbeds, and buried iron - maybe its doing the RSG thing by itself.