Aquaponic Gardening

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I'm hoping to find someone who is actually using the Growstones recycled glass media.  I'm very interested in it since it is a much more sustainably produced material.  However, a quick read of their website indicates that it may increase pH. Is anyone using it and what has been your experience?

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Thanks for the reply.

So whats your ph cause plantit its not neutral of what i read.


I have two  tanks with hydroton and two larger tanks with growstones and one tank with Plant!t.

I have not measured the pH for maybe two years


City water or well water out of a pipe is going to have a false low pH.  You need to bubble it or aerate it for a time to let the trapped CO2 escape to get an idea of what the real pH is of the source water.  This issue cause me no end of trouble before I understood it.  I couldn't figure out why my pH would always be way high when I was topping up with water that had a pH of 7.  Well that top up water only had a pH of 7 before the CO2 escaped, after the CO2 escaped the pH was actually more like 8.2 at that location.  See, CO2 dissolved in water acts as a weak acid which is why you get the false low pH reading right out of the tap or hose.

Most manufactured media is going to have an initially high pH from oxides that form in the kiln process but these will rinse away with the initial wash.  Other manufactured media may have calcium hydroxide or some form of carbonate used during the process which is likely to cause an initially elevated pH but this usually doesn't last forever or even very long.

Aquaponics is going to naturally have a dropping pH as long as there are no anaerobic conditions in the system causing the pH to go up instead.


Great to learn something new.


Glad to hear I'm not just sounding like a broken record repeating the same section over and over.

My source is rainwater.  I do not let it bubble.  The pH of the rainwater is slightly acidic.  When I started, however, we'd had no rain, so I washed the Growstones with chlorine-filtered city water.  (The city water around here is alkaline).  That was a couple months ago.  My plants all have yellow leaves with greenish veins, which indicates iron or manganese deficiency, usually due to high pH.  I have changed out much of the water with rainwater.

TCLynx said:


   What is the pH of your source water?  What is the pH of your source water after you let it bubble for 24 hours?  I would not expect to need to add pH down continually to a system with grow stones, at least I didn't.  Are you sure the problem is from the grow stones?  I know people have used grow stones quite successfully for hydroponics so I wouldn't expect it to have continual long term pH issues.


   Have you ever dosed your system with chelated iron?  If you are keeping your pH below 7 using pH down, then I don't know that I would automatically assume that all yellowing of leaves is due to pH being too high and causing nutrient lock out.  I ran a system for years with a pH that rarely got below 7.6 because the media was shells and simply dosing with DTPA chelated iron was able to fend off Iron deficiencies.  Even at the new farm where I am collecting enough rain water to let my system pH settle down at 6.5, I still have to dose with some chelated iron on a regular basis since my fish food and source water don't seem to be providing enough (I have an iron test kit and if I don't dose for several weeks the Iron level will be almost unreadable so I have been dosing enough weekly to keep the Iron reading up at about 2 ppm.)  I had far more trouble (and still do) with potassium deficiencies.

Iron Deficiency shows as yellowing of the newest leaves first while the veins stay green.  There are other deficiencies that can look a bit like it but usually starts on the older leaves first.  I have mistaken potassium deficiency for magnesium deficiency before.

Also, how much and what kind of food are you feeding the fish?  It is the fish feed where the nutrients generally come from and if you have been changing out lots of water, you may be just short of nutrients in general.  What are your nitrate levels like?


Thank you for your suggestions.  About a week ago I added chelated iron and the newest leaves are coming in more green.  I still have to add pH down almost every day.  The nitrate levels have been 80 -160 ppm.  I have few fish and they are small.  They eat little, but I had trouble with too much nitrite, which has now all converted to nitrate.  (The nitrite was left over from cycling.  I had been adding another brand of pH down which was apparently killing the nitrate-forming bacteria.)  The fish food is flakes made from fishery byproducts.

So out of curiosity, if you don't add pH down every day, what does the pH actually rise to?  It sounds like it is a rather new system so the truth is you may simply need a little more patience.

That seems like the best way to go, sit back and relax. after your system finds a balance, you will wonder why did you go thru all the worry.

Yes, it is a rather new system.  I will take your advice and not add pH down for a few days.  If the pH gets to 7.7, though, I think I will do something for the plants are not doing well.

Thanks for your help.

What are the ingredients of your pH down.  Seeing as you have been using it regularly to keep your pH below 7 AND your plants have not been doing well ANYWAY, it makes me wonder that you feel it is the pH that is making your plants unhappy.

Of course if the way you are using the pH down is causing the pH to bounce violently, that will make most everything in the system Unhappy.

Or if the pH down is an aquarium type pH down, it could be elevating your salt levels which could also make plants unhappy even if the pH is in what should be a good range for them.

Remember that I am coming from having spent years with a system where the pH really could not come down below 7.4-7.6 and I still had lots of plants that produced well though not as well as they might have given other conditions.

Treating an aquaponics system like a chemistry set or hydroponics system usually has more detrimental effect on production rather than what I expect most people are attempting to get to happen by adding this and that to "fix" what they think to be wrong and then not having much patience to wait long enough and see the effects before attempting to do another "fix" or doing too many things at once so it becomes impossible to know what it is that "fixed" the problem if anything.

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