Backyard Aquaponics
A place to discuss aquaponics

Hi all,
i've been monitoring my PH in the system and its always been very alkaline (8.. I recently started redesigning my build in order to relocate it, and started testing the water much more and trying new things. I am coming across some odd readings.

is it possible for the Ph test kit to be messed up? I'm guessing I'm doing something wrong as usual, but thought i'd ask. haha

so... fish tank water - 8.8
I replaced about 30% of it, and took readings about 12 hours later (next morning) - 8.8
I tested my tap water, 7.8
I tested a gallon of bottled water, 7.4

my grow bed has a mix of different media - lava rock, pebbles, and clay pebbles.

I then separated all 3 types of media into different glass cups... added bottled water. let it sit for 2 days and re-tested.

All 3 of them show a reading of 8.4

I don't get it... how can clay pebbles, lava rock, pea pebbles added to bottled water all show a reading of 8.4??

what am i missing? is there a better way for me to more precisely test this, or more efficiently bring the PH in my system down??

This thread should help:

viewtopic.php?f=1&t=21314&view=previous#p448276

Definitely helpful thanks. My system is still young and my constant re arranging and rebuilding is probably not helping. I'll move it to its final destination and then let nature take its course.

While I wait for Ph to drop naturally... Any suggestions on plants? I have maxi crop but not sure of how to apply it. Mix it in water and spray it on the leaves with a sprayer ?

Also, any thoughts on why all 3 media types would show the same ph reading? (If not user error lol)

My best guess is its your gravel thats the problem. I had a similar issue when getting my grow beds started. I bought some local 3/4" gravel and did the vinegar test. No bubbles after 10 minutes so thought all was good. Decided to make sure with leaving it sit in acidic water over night. Filled half of a 1 gal bucket with the gravel and the water at 6.4 PH level. Tested it in the morning and PH was 8.2. Ok I wasted that purchase and decided to go to a place where they crush up bedrock and did the same thing. Vinegar test with no bubbles, gallon bucket half full over night and same results. PH goes from 6.4 to 8+. Turns out all the bedrock on this island of the Philippines is all ancient sea bed. Meaning the rock is composed of compacted seashells every where I go. Which is why I am using strictly clay balls and getting pumice stone next month.

In your case, since you had them all together for awhile. Lava rock, gravel and clay balls. The calcium carbonate from the gravel has soaked into both the clay balls and lava rock and will take time to come out since both are very porous. Something you could try to make sure is get a sample of both and wash them with citric acid or vinegar to clean out any carbonates and rinse thoroughly when finished. Then do the overnight test with your tap water and see how the PH is affected. If you dont rinse the vinegar/citric acid good enough it will likely be opposite and be more acidic considering how porous both media are.

If I am correct then you can wash say half them both with vinegar and mix the other half to balance the PH swings until all the carbonates are absorbed or your nitrification process takes over and you are working to control low PH

Hope this helps

Chad

I would actually start by filling a glass with tap water, leaving it sitting out for at least 24 hours, and then testing pH - there's a very good chance that it contains a lot of dissolved gases* when it's fresh out of the tap, and that will artificially lower the apparent pH. Once they offgas, you can test for the actual pH, which I would bet is somewhere around 8.8.

Also, if you have hard water (i.e. it has lots of carbonates in it), that will buffer the pH up. So, basically what Chad is saying about carbonates, but originating from your water rather than your gravel. If you can collect safe rainwater (i.e. not off a galvanised roof etc!) and use that to top up your system, that will be lower pH and much softer water, and you should see your pH start to drop fairly soon; otherwise you may need to start dosing your topup water with acid to exhaust the carbonates and bring the pH down safely.

*(The gas in question is mostly carbon dioxide; dissolved in water it forms H2CO3, carbonic acid. It's a weak bond and the gas will dissolve out given a chance, you can speed things up by aerating the water.)

The other thing that may be a factor (and worth checking) is if you have chloramines in your town water supply.
That can create issues with test kit readings and system pH.
Quite common issue in parts of the US - various threads discuss it around here.

search 'chloramine'

as Mel says - leave your water for a few days and see what readings you get.

some aquarium places test water and can give you a range of tests - including KH and GH.
(that address the hard water aspect). But first just store some water, let it gas and see what happens.


>> While I wait for Ph to drop naturally... Any suggestions on plants? I have maxi crop but not sure of how to apply it. Mix it in water and spray it on the leaves with a sprayer ?

yes it needs to be pretty diluted and applied morning/evening.

actual concentration depends on brand - as you are in USA Scotty435 would be best to advise - he foliar feeds.
(it is something I have never quite seemed to get right - but some guys here do it well)