Backyard Aquaponics
A place to discuss aquaponics

I've had an ongoing battle with the pH in my system (over the past 6 months). My tap water is very high pH (8.4 - 8.6) and it's what I filled my system with. I figured that after my system cycled the pH would drop and I would have to add shell grit, limestone, etc. to keep the pH from going to acid... but it's never quit gotten there. I started testing things and I think it may be my gravel. Here's what I did and tell me if you think I'm right.

Tested tap water: pH 8.4-8.6, Carbonate Hardness 3 (on the german scale).
System water: pH 7.8 mornings, 8.0-8.2 late afternoon (algae taking co2 out of water I'm guessing), Carbonate Hardness 5.

I thought it was a little suspecious that my system has a higher carbonate hardness then my tap water. Especially since I was injecting CO2 into the water to bring the pH down. The other effect of injecting pH into the water is that is lowers Carbonate Hardness.

I took a gallon of water from the tap and added 3 mL of vinegar (5%) to it and it brought the pH down to 6.8 and the carbonate hardness to 1. I then got about 2 cups of the same gravel that's in my system and poured it into the gallon of pH 6.8 water. I stir it up for a few minutes and test the water again. The water is now pH 7.8 and the carbonate hardness is up to 4 - 5. Arg. Have I been fighting my gravel medium the entire time instead of the buffering capacity of my water. Shoot me now. I poured the gravel into a bowl and poured vinegar into it... bubbles.. bubbles... bubbles... arg.

Hey MrG, do the plants show any deficiencies with this pH? Other than higher nitrite toxicity why not just live with it (unless the plants are showing problems)

everything looks horrible. the plants look grotesque and deformed... the lone tomato plant has curled purplish leaves. I know toms are heavy feeders but there really isnt that much planted in the system. The bean plants are yellow with dead brown spots on the leaves. If it was just 7.8 then I think I might be able to make it but during the day when the plants need the nutrients the most the water will push 8.0 pH, locking out even more nutrients during the hight of photosynthesis. I think the algae is getting to all the nutrients before the plants are able to.

Have you taken steps to address the algae problem?

Will re-check your system thread later...

MrG,
My water comes out of the tap at 8.4 and the LFS treats water to 7.0. Had major problems getting tropical fish to live until I changed where I bought the fish. They came from 7.8 and did fine as I acclimated them slowly. I say that to make this point; that trying to adjust pH down is a never ending battle and the changing pH can do more harm than the high pH.

Our AP system is 3.5 weeks old and doing great. The pH on it is stable at 8.2 with a GH of 2 and a KH of 14. The tomato, lettuce & mint cuttings are growing like crazy.

I may be totally off base and of no help at all, but I do wish you lots of luck in solving the problem.

Tap water 8.4 - 8.6 ,, FAR-OUT ,, how the heck do you wash yourself.

Firstly don't worry about the buffer , that just tends to slow down changes and is beneficial.

I'm still in shock ,, never heard of tap water with that high a PH.

The sissling on the rocks definately suggests a chemical reaction ,, acid + alkaline = salt to water +. Was the gravel still wet when you tested? The only rocks I can think of that would be VERY alkaline are also very soft and crumbly or Volcanic rock.

I'm guessing , so I'll leave it to those that know a lot more than me.

I think ultimately you may have to work out how to change your tap waters' PH .. there is a filtrsation methos that does it,,,I'll try and find a link to that.

8.6

dgrdalton - my fish love the pH. They all come from the colorado river which is also the supply for our city water. The water from the tap comes out a little higher pH then the river... I think because the city takes the CO2 out of the water before they send it down the pipes. So, my fish are prefectly happy with the water.. it's just that most plants can't take a lot of the nutrients out of the water then you approach 8 pH. Let me see if I can conquer up that nutrient/pH graph...

for hydroponics


for soil


I don't know... you say that your pH is 8+ and your plants are thriving.... maybe I just haven't had enough fish in my system. I just doubled the number of fish from 15 to 30 a few days ago but they're all small fish about 3". It's still a light load for a 300 gal tank and 150 gal of grow beds. Then again ammonia, nitrite & nitrate never budge from 0. What really makes me suspect it's the pH and not the nutrients is that for awhile the beans where growing really well. I had a CO2 fermenter (sugar water/yeast) set up pumping CO2 into the tank. This kept the pH close to 7.8-7.8 for a couple weeks and then it ran out of steam... or sugar as the case may be. When the CO2 slowed down is about the time the beans all went to hell. Perhaps it's a case of low nutrients from the fish exacerbated by the high pH...

Rupert -

I've tried to deal with the algae but I have to admit I've made little progress. The tank is shaded as much as possible from the sun. I tried to add duckweed to shade the water but my goldfish just eat it. I might have to get rid of the goldfish and try again.. I don't think the bream will touch the duckweed. I set up an extra pump a couple days ago just for extra airation... it just pumps the water out of the tank and sprays it in a fan over the tank back into the water. I've read extra airation is supposed to help with algae contol. In the two days it's been set up I've not noticed much difference in the amount of algae. Maybe my system is just now cycling after 6 months because it's been cold and the fish haven't been eating/producing nutrients?

The bubbling gravel is probably limestone. I'd say part of the pH problem is that you indeed have been fighting your growbeds. However, I also think you have a point about the algae getting all the nutrients before the plants. What nitrate do you run? Consider supplementing with chelated iron (which has a lot more than just iron in it) for a couple weeks. Then you could figure out whether it's lack of nutrients over all, or locked nutrients.

Post pictures on your system thread, maybe it is more to do with watering levels or something like that. Did you use a high pH test for the over 8 tests?

I fiddled with pH a lot in my first system and I think it killed a lot of them (all 60 died eventually).

Yeah, think I'm tending toward Janet's hypothesis ... limestone growbeds...

Makes sense given your in major limestone country... and the fact that you saythe county bubbles off CO2 from the water supply... and your own experiences of adding your gravel to water that is more acidic than the growbed media....l leading to... bubbles...

Tony from WA had exactly the same problem....

At pH 8 your beans (and most leafy things) should be growing well.... leafy things like nitrogen, as do most young plants... and pH 8 is fine for nitrogen uptake....

Unfortunately though at that pH you're locking out the essential trace elements like potassium and iron that your beans and other things need for flowering and seed (bean) set and growth....

I wouldn't bother with adding CO2, that's for sure....

Is your duckweed growing and thriving??.... if so then there is ammonia present... duckweed loves ammonia....

Perhaps, with your lower temperatures, pH, and duckweed sucking the ammonia.... maybe you haven't truely cycled as yet....

Any nitrates being produced (i.e. converted nitrogen) are/have been sucked up by your beans.... and your tomatoes, another heavy nitrate feeder.... and your algae, a great ammonia/nitrate converter/user....


Things to try....

Use a bubbler and sunlight (and/or an aquarium heater) to help offgas the CO2 from some tap water.... enough to do several water changes.. i.e 100 gallons at a time..

Do several 30% water changes to effectively replace the system water... beware of temp change if you heat the tap water... don't introduce when hot...

This should bring the pH toward 7-7.5.... and get rid of most of the existing algae...

I'd rip out the tomatoes and beans....and the duckweed...

If possible heat the tank..... definately aerate the tank as much as possible to help keep the algae from reforming...

And see if you can re-cycle..... You should at least see an ammonia spike...

How much are you feeding? ... if you don't see any ammonia after a day or two.... try upping your feed slightly each day until you do....then stop, even don't feed if the ammonia keep rising... watch for the nitrite spike....

Test daily and post results...

Other ideas, opinions....??? Oh and if you have any water plants, like lillies... pull them out asap...

Forgot to say...... before doing anything else.... you could try adding phosphoric acid and seeing what effect that has on your existing plants....

Plants could be too far gone by the sound of it.... and it'll probably play havoc with your algae...

Phosphate, nitrate and warm water.... blooming heaven....

Perhaps try the phosphoric acid later

Agree with Rupe, sounds like a phosphorus deficiency at that ph, and compounded by the algae. The stunted deformed growth makes it likely. Are the fish aside from the goldies plant eaters? Would shade the tank more if possible, not get rid of the goldies, I am unsure that aeration in the way you are doing it would get rid of algae. Barley straw is supposed to work but never tried it, UV sterilizers do (but slow).
If there is any way of foliar spraying Phosphorus might work.
UPS is going off like a two bob watch have to go, and hope this makes sense

I have a milder version of your problem. I used shells as a major portion of my grow bed media. Since then, I have not seen a pH in the systems below 7.6. Luckily, my well water is about 8 after outgassing and I know that in a system without shells or limestone, the pH will eventually fall even with my limestone aquifer well water.

Anyway, My plants showed plenty signs of Iron Def. (yellowing new leaves with green veins.) Adding Iron to the system water was not overly effective since the pH was a bit too high for the plants to make good use of it. I had better luck with foliage spraying so long as I didn't mix it too strong.

Another Def to watch out of (which you mention of purpling leaves makes me thing might be the case for you) is potassium. Even though the high pH makes potassium uptake just fine, that doesn't mean there is any potassium to be taken up. Some people bury a bit of banana in the grow beds (without peals I think as they are likely coated in pesticides.) Other people use potassium bicarb to keep their pH up. Many people use a seaweed emulsion spray. I've gotten fish safe potassium supplement to add to the system. I've even heard of people using potash as a pond supplement but do be very careful with that one as it could have major pH effects.

Your plants could also be having problems with phosphorus uptake due to the pH. Since most fish food has enough phosphorus, you don't want to add it to the water. You might Look into ways to foliar feed it but be careful not to over-do as the system probably doesn't need more in the water. If you are getting plenty of green leafy growth but your plants don't get into flowering, then I might say try the phosphorus but otherwise, I doubt that this one is your problem.

Back to the pH issue, yep you are probably battling the media in your grow beds if it is limestone gravel (most really cheap gravel is in many areas of the country.) I'm not sure what is best for you to do. If you were planning on adding more grow beds in the future, I would tell you to get something like river rock for the future beds. I just ordered more media for my monster grow bed and I went with straight river rock. (River rock around here is generally mostly quartz type rock.)

Good Luck!

I may have a high pH related problem, also. My plants are growing well, but my first little bloom on one of the tomato plants fell off this evening. Our lake here is created from the Brazos River which has a high salt content and I am assuming is the cause of the 8.4 pH of the tap water. My dad waters his dirt garden out of the lake and has no problems with his veggies, but the charts MrG posted above show that his plants are probably getting nutrients from the soil that aren't in the water.

Very interesting. Thanks for the ideas given in this thread as they will probably help me also as my system ages.

I'm going to try and answer as many questions as I can here... hope it doesn't sound to jumlbed. I feed the fish 2 or 3 times a day and I feel like I feed them quit a bit. I don't feed commercial feed though, I raise and feed them almos exclusively soldier fly larva and red wigglers. The tank is about 30 sunfish (breem) and 2 goldfish. So the goldfish are the only veggies. I can't keep duckweed in the tank because the goldfish slurp it down faster then it will grow, so no worry their about the duckweed taking up nutrients (or shading the algae for that matter). Even with the amount I feed the fish I have NEVER registered ANY ammonia, nitrite or nitrate. Like I said I just doubled my fish population (to 30) and was planning on adding another 15 in the next week or so. I figured with 300 gal water, 150 gal media, I should stock 30lbs of fish to fall inline with the 4:2:1 ratio. My 30 fish aren't anywhere near 30 lbs. Even if I add another 15 there won't be anywhere near 30 lbs. I just went and check a chart of 'standard bluegill weight by size' and at 6" they would weight 0.2 lbs.. so my 30 bluegill at 3" would weight maybe 0.1 lb each(lets be genereous) equaling 3 lbs. Very low compared to 30lbs... hmmm. a Maybe that's just my problem, not enough fish poo... Oh, ummm I use a high pH test (7.4 - 8.6).