Aquaponic Gardening

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I noticed this morning during a regular water test that my pH is somewhere between 6 and 6.2...color charts never quite match what's in the tube, lol.  My pH usually hangs out between 6.8 & 6.6.  I haven't changed anything in awhile.  Its been about two weeks since adding any fish, and a week since I added worms - and besides a small ammonia spike when that happened, the other water parameters have stayed the same.  My ammonia reads somewhere slightly above 0ppm (its been slowly coming down since the spike, and fish are fine, so no worries), my nitrites are 0ppm, and my nitrates are somewhere between 10 - 20 ppm...they were staying steady at 5ppm but have gone up since adding fish.  


No fish have died, they haven't changed behaviors, and my plants are huge and flourishing...I even noticed my first tomatoes this morning.  I'm not so much worried that I have to change something, but am curious what could be making the pH drop all of a sudden? 


I don't have any rotting wood in the tank, no decomposing fish, there are occasionally some dying leaves in the water...but the snails eat them within a day or two and they have always been doing that...there is plenty of water flow, I can't think of any other reasons for the drop.  


The only thing I've noticed is a slight increase in the amount of brown algae growing, but I was attributing that to the nitrate spike as I've always had some, but it got to be more after adding fish.  I just cleaned that off the glass this morning.

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Hi Ricky.  pH will naturally drop over time in a healthy system - all is good!  You should buffer it back up though.  The first rule is: Whatever you do to adjust pH in aquaponics – Do it slowly! Fast, large pH swings are very stressful on fish and will be much more of a problem than having pH that is out of range. Target shifting your pH reading no more than .2 per day and you should be fine. Raise pH either by using “pH Up” or by alternating alternatively use calcium hydroxide – also known as “hydrated lime” or “builder’s lime” with potassium carbonate (or bicarbonate) or potassium hydroxide (“pearlash” or “potash”).


Hope this helps.


Thanks sylvia...that does help, as I couldn't think of anything else that might be happening.  I do know not to do anything to make it swing wildly.  Thanks for the link on the pH up - I think I've seen it at my local hydroponic store...are there differences in products (read as, "what should I look for that isn't fish safe?") and how long does the "pH up" help stabilize? or does that depend on my buffering capacity?
Sorry, my friend.  Buffering specifics is beyond my chemistry skills!  The pH Up product is safe for fish and plants, and, yes, it can be found in hydro stores.

There are other slower options for buffering (however because they are slow you need to be careful not to over do it)  Many people will use plain calcium carbonate (could be garden lime, shells, coral sand etc.)  My method when I need to buffer is to hang a mesh bag (some people use stockings or panty hose) with some chicken grit or shells in the fish tank or sump tank.  If the pH goes too high, pull it out.  If the pH doesn't come up quick enough use a small dose of the products Sylvia listed and then use the buffer bag to help buffer long term.


Of course if you are not alternating the calcium and potassium hydroxides you might need to add some other source of potassium.

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