Backyard Aquaponics
A place to discuss aquaponics

Hello, I would like to try and bring down the Ph of my system by using eggshells, has anybody tried this? If so could you give me some advice, please.

Egg shells and other shells buffer the ph. If the water gets acidic as it will due to nitrification the shells act as a buffer to bring the ph back to 7 or so
I use shell grit in my systems for this

so what does that mean for a PH that is high, will they also act as a buffer in this instance?

Sorry I forgot to ask what do you do to the eggshells before using them? Do you just crush them and mix them into your media?

No eggshells will only buffer it up. They will do nothing above 7 ph.

OK, thanks for the tip, I'll save the eggshells for later, by the way how do you use yours? Do you just crush them up and mix them in your media or do you have to prepare them in some way first?

If you mix them in your media you might have problems of high Ph down the track and you won't be able to do much about it...
Whatever you do keep them separate.
I tried egg shells but found they had a very slow response. I just use builders lime, fast response and cheap as chips.

What is your PH?

All shells are carbonate buffers and will slowly raise your PH to approx 7, at that stage there is no acidity as a PH of 7 is neutral and will no longer buffer.

Acids like HCL are used to bring PH down.

If you do need to buffer your PH I would use shell grit or cuttle fish before egg shells as they are a little easier to manage. But if egg shells are abundant and a better choice for you, wash them in boiling water, strain and then put them in a panty hose leg or some kind of fabric bag and either hang it in your FT or sit it under your water supply to the GB.

does anyone else find there fish nibble at the sock/pantyhose ? I had my shell grit in a sock in with the silvers though a few holes appeared in the sock and now i've got a fair bit of shell grit in the tank floor.


I buried egg shells under my tom plants - not specifically for ph, more for calcium to address blossom end rot.

I'm thinking of going over to cuttlefish bones and lobbing a few in the fish tank - the silvers seem to like to have something to cover under.

So the eggshells can fulfill more than one function, I like that maximum utilisation of product.