Backyard Aquaponics
A place to discuss aquaponics

If you original gravel had limestone or Marble, I would guess that was part of your problem. From your description of your gravel, I'm not so sure though.

Have you tried pulling some tap water and letting it outgas or put a bubbler in it for a while then test the pH and see what your tap water gives you? Just to know for future reference.

Or you could try and even it out by putting something in that naturally brings the pH down. People have used various methods, search the forums. You could try putting a bag of pine needles or similarly acidic medium in your beds in an attempt to counteract the pH shift up.

You could have a drip of HCl going into the sump water. A lemon, some kind of straw (I forget which one), vinegar etc etc.

You really REALLY want to make sure it's the grow bed media and not something else before you go replacing all those rocks....

can you post a photo of the rock in full sun? Dry & Wet

here you go:

I'd say it was limestone...

these folks are rock crazy http://www.sagamoresoils.com/gravel.html

a pic from their website; they have many


it could be some kind of marble chip or lucky stone also


looks and act like limestone but I'm no expert! there are some here however, they'll chime-in and correct me.

It certainly does look like it doesn't it. What a bugger Nico.

Yes it looks a lot like it. And this was the only gravel I could get here. Maybe I'll use Seramis although it is quite expensive.

I think some one was experimenting with using a mix of limestone or marble chips along with coco coir or peat moss to see if it would balance the pH between the two. I'm not sure I've ever seen any conclusions about that trial though.