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My 8.5 PH has not dropped for 7 weeks of fishless cycling. Have hoped it would drop as have heard many times will be high for cycle up. Yesterday added fish. Have been running with low ammonia and Nitrate 40ppm. Seems to be cycling through good. My tap water is 8.4, when I originally tested it was 7.4 so though I would be ok. My river rock did not foam up with vinegar when originally tested. Have added muriatic dosing to drop ph about .2 ocassionally. Yesterday dosed to 8.3, today down to 8.1. Will probably buffer back up though. My ferrocement tank is pool painted so should seal? With luck maybe will drop later as I've heard theses systems can run high at first. Had algae 1 month ago, pretty much gone since then. Any ideas or input appreciated? Hope I'm not dead in the water after all this project build.

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Can you start collecting rain water for your system.  There is a good chance your tap water is just really really hard and topping up the new system is probably keeping the pH high.

 

My tap water (which is well water out of a limestone aquifer) will keep my systems buffered up to about 7.6 when I'm using lots of well water for top ups.  If I switch to using rain water to top up my pH will actually drop to the point that I have to add some buffers back in (like alternate adding some potassium bicarbonate  with using the well water to top up on occasion to keep it buffered to about 6.4.)

Thanks TC, I'll have to hurry as the rainy season is about over. Have thought about this but need a tank and to build some rain gutters and have been away for awhile now. I keep my PH meter in a plastic jar with water, and that waters PH has dropped to 7.4 over 7 weeks time. Then again I haven't been topping off that water. Any chance of my pond dropping? Maybe slower because of the large volume?

Aquaponics naturally lowers pH so unless there is something in the system that is buffering the pH up, it should come down in time.  The harder you work the bio-filter the faster pH tends to drop but if you are topping up with really hard tap water you are essentially adding the buffers in that way so the choices there become, 1-use rain water or 2-soften your water or use an RO filter.

 

When you have adjusted the pH using acid, did the pH always just come right back up the next day?  Or did it stay down until you topped up the system again?

Hi TC, By work the bio-filter I'm thinking your saying some good doses of ammonia and high levels of nitrite? I've been putsing around with low doses. I'm using twice the volume of water I planned to start with, because of the way project all tied together Thought I could find some ammonia here but haven't found any yet. Any idea approx. what percentage rainwater would be needed? The RO filters I looked into seemed to use quite a lot of water. The water soften idea is new to me, any idea how? I will get some bottle water and test my rocks again.
PH seems to come up pretty quick maybe a day or 2, I'm afraid that answer is not good for me.
TCLynx said:

Aquaponics naturally lowers pH so unless there is something in the system that is buffering the pH up, it should come down in time.  The harder you work the bio-filter the faster pH tends to drop but if you are topping up with really hard tap water you are essentially adding the buffers in that way so the choices there become, 1-use rain water or 2-soften your water or use an RO filter.

 

When you have adjusted the pH using acid, did the pH always just come right back up the next day?  Or did it stay down until you topped up the system again?

I don't have numbers because it depends on so many things as to how much rain water it would take.  Do you know how much water you top the system up with?  I know that if I use rain water to top up my 300 gallon system for a month the pH definitely drops compared to if I'm topping up with my well water.

 

Now I know of people who say they have done things like add a couple oak logs (like pieces of fire wood) into their tanks to help lower pH.  I'm testing that idea out on one of my systems right now but It hasn't been a week yet so I'm not seeing any results.

 

A water softener that removes minerals from the water (like for keeping lime scale from building up in your water heater and such) can work but it will likely also add some salt to your water so it may not be that great.

 

RO filters can be costly which is why I haven't gone that way myself but I'm having issues with lack of rain too.

I tested my gravel in bottled water PH 6.5. After 12 hrs. was up to 7.2, after 3 days 7.4. So seems my gravel is good. Now after several doses of rainwater and enough muriatic for a .1 drop. I'm still at 8.3. Seems either the ferrocement tank did not seal effectively with the pool paint 1 coat. My well water just way too hard. Or hopefully its something in the system cycle up holding it high for now. Will anything grow in ph 8 system? Any other ideas ? Thanks!!

if the weather is cool, I hope you like water cress.  Granted my system was 7.6 but watercress went mad last winter for me.  In summer I seem to do well with water chestnuts in full sun and several inches of water over the gravel in a constant flood bed.  I've managed to grow bananas to the point of cracking grow beds in that 7.6 system as well.

Coming to terms with the idea I may have to empty everything and maybe another coat of pool paint uhg! Stuff is over 100 a gallon here which is why I only used one coat, it did seem to cover well.
If you are using concrete you may need to create a barrier between the concrete and the water to prevent leaching. I do not know if paint is the best product to use. When I had the same problem with my ferrocement tanks I had to drain the system and coat the concrete. I found paraffin to be the best and cheapest option. I melted the paraffin in am old pot and painted it onto the concrete. Then melted I the paraffin into the concrete with a torch. Now water beads off the sides of the tanks and I have never had a pH issue since.
Thanks Chris, The odd thing is I just poured Muriatic on the side of the tank in a few places and it did not foam at all. The test on the paint tells me its sealed cause ya know what happens when acid hits concrete. Whereas what I spilled on the gravel did. But I tested the gravel with bottle water and it only came up to ph 7.4 after 3 days. There are a very few pieces of clay like crumbly stone that really fiizz with acid. This ph part is quite complexing.

Chris Smith said:
 If you are using concrete you may need to create a barrier between the concrete and the water to prevent leaching. I do not know if paint is the best product to use. When I had the same problem with my ferrocement tanks I had to drain the system and coat the concrete. I found paraffin to be the best and cheapest option. I melted the paraffin in am old pot and painted it onto the concrete. Then melted I the paraffin into the concrete with a torch. Now water beads off the sides of the tanks and I have never had a pH issue since.
A small amount of stray limstone or marble or marl clay hiding in with your grow bed media can really cause you havoc.
I wonder if you could go through and isolate one bed at a time and give it an acid water treatment to dissolve away the unwanted calcium carbonate then make sure to dilute the acid water well before draining it away.  Would kill any plants or bio-filter already built up in a grow bed but if you have several beds and not too many fish.  Maybe you could take one bed offline for the treatment every few weeks (to let the bio-filter re-establish in the treated bed for a while before taking the next one offline.)  Would be a pain though maybe not as much of a pain as replacing gravel.

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