Backyard Aquaponics
A place to discuss aquaponics

So I was extremely foolish and I bought some gravel after I asked the people at the building materials place if the gravel was produced from granite. I thought this would be okay and didn't test the gravel until now. My tap water is a bit alkaline at 7.4 and after leaving some gravel in a bucket full of the tap water for 24 hours the PH bumps up to 8.0. Can I work with this? Is it possible to buffer the water by adding shell grit or something? Or will it forever buffer to 8.0 (or maybe even higher, I'm going to test it again tomorrow).

Also, the bucket I used had a lot of dust and dirt in it but I scrubbed it pretty clean with a brush but there were still areas where the gravel had scratched the plastic and I'm wondering if that might have had anything to do with the bump in PH...

Edit: not shell grit as that buffers it higher right?

Will the acidification due to nitrification bring the levels to a reasonable level once I get everything cycled? Thanks for any advice!

if the gravel contains limestone it will buffer high.

is it Blue metal?? if so it will buffer high for a long time until the nitrification kicks in then it will come down naturally.

i used blue metal and worked with a PH of 7.5-8 for a long time, affected plant growth, plants going to seed etc, but now it has come down to buffer at around 6.8-7 and doesn't move at all. the use of chelated iron can help with nutrient lockout to plants, as a high ph will lock out the nutrients and affect plant growth. also found that keeping the system dosed up on seasol or similar until it buffers out and cycles up worked well too.

some media's will buffer low, which is obviously more harmful to the fish and can be more work to handle as the natural cycle is to become more acidic.

OBO & others started with pH up around 8 and it comes down. You don't know that it's not just some carbonate dust on the rocks. So if you're REALLY worried, add HCL to bring it down and see what happens, if it shoots back up you might be in trouble. It's obviously better to add acid if there are no fish in there (you don't want to pH bounce!).

I'm in the process of testing a bunch of gravel samples from different quarries. Glass of water with a table spoon of vinegar brings the ph down to about 4. Add gravel and leave for a while.

One gravel shifted the ph up to 9 all the others were 8 or less.

I'm in the process of testing a bunch of gravel samples from different quarries. Glass of water with a table spoon of vinegar brings the ph down to about 4. Add gravel and leave for a while.

One gravel shifted the ph up to 9 all the others were 8 or less.

Thanks for all the replies everyone, it is much appreciated.

Jamey:


I specifically asked the suppliers whether this gravel mix contained any limestone; they specifically told me it didn't and was produced from granite.



I forget what this called in the states but the stuff I got is 3/4 inch crushed gravel; the suppliers said the stone is granite. I'm really hoping that this is the case and that after I start cycling the PH will stabilize.

Gemmell:


I'm hoping this is one of the possible reasons for the high PH, thanks for the advice I will try this.

Stuart:


How long should I leave it before I test it? I do have a jar of gravel and vinegar that has been sitting for a couple of days but I put in a lot more vinegar than a table spoon.

Thanks again to everyone for the replies.

hay a tip about your tap water. IF you checked the pH right after you drew the water from the tap, that was a false low pH. (if I test my water right out of the faucet, it usually says 7 but it's a lie, if I were to let the CO2 outgas and then test the pH again it is usually over 8!)

So, your high pH might not be due to the gravel at all!!!!!!!

I recommend rising some gravel well and then putting it in some distilled water. leave it for a few days then test the pH again. You will probably be fine.

Here is what I did before fishless cycling up my newer 300 gallon system. I made a point of getting river rock this time. I washed the media and filled the system and got it pumping around. Then I used some pool acid to bring my water (well water from a limestone aquifer with a pH over down into the appropriate range. It took a few doses to get the pH down to 7.2 and it would still pop up to 7.6 but I know that a system can cycle up and even grow plants with a pH of 7.6 so I left well enough alone and started fishless cycling with my pH at 7.6. Guess what, the pH of that system dropped way down and I've been having to keep a mesh bag of limestone chips hanging in the fish tank to keep the pH from dropping too low now. If I have to top up too much with well water and the pH climbs, I can pull the buffer bag out for a few days. It is important to keep your buffer material in a form that is easy to remove if the pH climbs too high. (My mistake with my big system is using shells as media, that system took two years to get below 7.6, lowest I've ever seen it was 7.0 this past summer.)

Check pH often since if it drops too low, it can stall the bacteria. Most people recommend adding buffer or lime if the pH gets below 6.5. It will eventually happen for you.

TClynx

Thanks so much for the info! I am gonna run out and test that theory out right now and it would make sense because a ph test I ran with a less detailed testing kit did show similar ph for the before and after. And the ph test I ran with the new kit was straight from the hose. Thanks so much for all the advice! Will report back.