Backyard Aquaponics
A place to discuss aquaponics

I have a 100 gallon FT with 3 split barrel GB that has been up and running for 4-5 months now. I have a dozen gold tilapia and a couple koi in the tank. My system has cycled and I have had stable water readings with the except of pH 8.0-8.2. I was told to just wait and be patient and as the system matures the pH with lower naturally. This just isn't happening. Part of my problem is my local tap water that I use to top the FT off with has a pH of 8.0 right out the tap and 8.2-8.4 after sitting a day and offgassing. I don't really have any other water source for topping my system off, I live in a hot dry area with little rainwater for collection. I tested a local river and the pH is 7.8-8.0, no use to me.
I've added a large sunken drift log to my FT for the last 2 months, but that didn't do anything for the pH. I do have plant growth, tomatos, basil and green onions are going fine, actually harvesting a couple ripe roma tomatoe each day. Lettuce, cilantro, chard, beans, eggplant and cabbage not growing past seedling size, then stay that size forever.
In order to get my vegi growth going I need to lower my pH hopefully down to 7.0 or so.
I do have hydrochloric acid available, but was hoping to find someting a little less harsh and scary to use. Is there anything I can use or add to my system that will help lower and help buffer and keep my system around 7.0? If not how much HCL should I add to a 100 gallon FT with 75 gallons of GB?

Thanks,
Cory

BTW, I did try to do a search for high Ph, but it kept excluding the pH parameter saying the search word has to be 3 or more letters.

Try 5ml of the hydrochloric acid... then retest pH about 2 hours later... this will give you an indication of how many points of pH you have moved...

You probably don't want to move pH more than about 0.4 in any one hit.... or day...

Add another 5ml a couple of days later if required...

I did use HCL in my system when I was first cycling it without fish. It took 30 ml of HCL to go from 8.2 to 6.8, but then it just drifted back up to 8.0 within a week or so.
Am I going to have to keep adding a weekly dose of HCL to keep it down at 7.0? Is there anything I can add to help buffer or bind the alkalining agents in my water? That where I tried a sunken log as I heard it will leach tanic acid into the water, but didn't do much for me other than give the fish a place to hide.

Cory

Forgot to ask, where should I add the HCL? In the FT, diluted first of coarse, or divided among the 3 GB after diluting? Will Maxicrop (Seasol) or chealated iron help with lowering pH? I haven't added either as I kinds remember that iron can't be absorbed at high pH and wanted to get my pH under control first.

Cory

Add directly to fish tank... under the water return... no need to diluted...

Maxicrop and/or Chelated Iron will not affect pH.... although, as you say, the pH will inhibit the take up of trace elements.... even in chelated form...

What is your media? Could it be affecting the pH of the water? My well water is rather high pH. 8-8.2 usually after outgassing. I did find that with inert media, a system using my well water will have a falling pH. When I filled my system with shells, my system stayed at 7.6 for over a year before falling just a little bit and now the pH will fluctuate depending on season and rain fall.

If you get your Grow media if rock/stone and put some in a container with vinegar and if it keeps bubbling then the rock is limestone base....limestone makes the ph go up....if so, then it is time to change grow media ... . Hope this helps

Can only give yon my experience, (I'm sure one of the guys here will be able to correct me.)
An excess of nitrate creates nitric acid when operating within the nitrification process.
this should lower your PH.
of course if you have a lime stone base media it seems that you may have some issues. No matter what you it will continue to break down your media.
what have your readings been lately?? eg. amm, rites, rates, ph water temp??

regards
Matt

My grow media is black cinder, I think you guys call is scoria, but its local Big Island volcanic cinders. Definately not limestone. If I had to guess I would think that cinders is on the acidic side since it is expanded with all those volcanic gasses like sulfuric acid.

Cory

My last reading I took last night was pH 8.2 amm 0 rites 0 and rates 5, couldn't tell you tempature of the water but I live in a pretty stable climate with highs in upper 80's lows at night mid 60's. My water looks very clear, no algea bloom going on.

Cory

I use red scoria (volcanic rock) in my case the rock always buffers to 7.4 till the system has aged. I have adjusted it down with a combination of dry acid and hcl but it does seem to drift back up again and surprisingly quicker in the system with more plants. Both of the systems I am adjusting are less than 6 months old and the pH has made a distinct difference to the plant growth.

I too have the same problem. My tap water is 8 and after resting would be more like 8.2/8.4. I tried the HCL adding various doses directly under the inlet pipe but always just buffers back to 8.0/8.2. It takes sometimes 12 hours to return (had a PH of 7.6 for half a day then 8.0 again the next morning.
Have been told that once my system cycles it should naturally come down but your saying your system has cycled.
do you have anything else in your FT? I have some blue rock screenings in the bottom of my FT and have been told to remove them as there is no advantage to having it in the FT. I'm yet to remove it but my system does seem to be starting to cycle properly now so I will wait and see if my PH comes down naturally.
Also someone suggested vinegar instead of HCL but seeing as the HCL was not working for me I am guessing the vinegar would have a lesser affect.

No my system has cycled properly. I cycled several doses of humonia before adding the fish. I got the appropiate spikes in ammonia, then nitrites, then nitrates, than all settled back down to zero.
The only thing I have in my FT is a large chunk of sunk driftwood that I was hoping would leach tanic acid into the water. There is also 2 10" terra cota pots for the fish to hide in. There is some fish waste on the floor along with the occasional errant leaf, some dropped cinders and an occasional dropped tomato, but its pretty clean and I can easily see the fish swimming on the bottom.

Cory

Hum.

Perhaps time for some experimenting.
What happens if you take a bucket of tap water and bubble it for a day then check the pH and note it down. Then mix some measured about of the acid into the bucket of water. Mix well, wait 20 minutes or so, mix again and measure the pH, note that. Leave the bucket of water bubbling over night. Mix and measure the pH in the morning. I'm curious if the bucket of tap water will re-gain it's high pH overnight.

If so, perhaps we need to start researching ways to precipitate out the buffering agents. This might be one of the few situations where a water softener might be appropriate.

Ah a mission! I will give it a go today and post the results in a couple of days. Do we have any methods for buffering PH down. I know this question has been asked before but maybe while I'm doing my experiment someone with a scientific mind could research this, we know that shellgrit will buffer a low PH to a usable Ph but what will buffer a persistantly high PH to a usable Ph.