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I want to make sure everyone knows that the pH of your tap water immediately after you draw it from the pipes, may not be real pH of your tap water.

This is some info that I didn't originally know it is caused me all sorts of confusion. Water from the pipes or well is often depleted of O2 and full of CO2 the carbon dioxide in the water forms a weak acid which will give a lower pH to the water if measured right away. If you take that same water and let it air (run it through a system or put it in a bucket with a bubbler) to let the CO2 escape then test the pH again, the pH will often be much higher. Example, my well water comes out of the tap with a pH of about 7 usually and after outgasing, it will have a pH of about 8.

This is important to know when doing water changes in a system that is likely to settle with a much lower pH or if dealing with a system that is not fully cycled and you are having high ammonia since higher pH makes ammonia more dangerous to your fish.

It is also good to know this info about tap water when dealing with pH balancing issues. If you are trying to hold a pH around 7 and adding lots of tap water causes pH to go up, then you want to keep water changes and additions small so the system can bring the pH into line without lots of bouncing.

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Thanks! This is good information.

David
You're dead on TCLynx, esp. with well water from certain areas. Another pH issue people should be aware of is the effect of afternoon algae blooms on pH. Although my tap water is really stable, I used to have major issues with pH swings in the afternoon as algae consumed all of the CO2 in my water. Now I use UV. Woo Hoo for UV!
Yes, algae can have major diurnal effects on pH. And!!!!!! If algae is having that extreme an effect on your pH, it could also be robbing your system of dissolved oxygen overnight and your fish could suffer for it. So, if you do have an algae problem. Please do some pH tests at particular times of day to find out if your algae problem might be severe enough to kill your fish. Do a pH test just before dawn or as close to it as you can. If the algae problem is severe, the excess CO2 in the water will be acting as a mild acid and bringing your pH down. Then do another pH test in the late afternoon before dusk. Then compare the numbers. If the algae is causing there to be a drastic difference between your dawn pH and your late afternoon pH then it could be a big enough algae problem to endanger your fish for lack of dissolved oxygen early in the morning. Because like all plants, at night algae use Oxygen and give off CO2, they only give off Oxygen when it's light.

If the algae is a big problem, the cheap solution is usually complete shade for any tanks until the problem subsides. UV also works.
Shading is cheap, but UV is awesome. : )

TCLynx said:
Yes, algae can have major diurnal effects on pH. And!!!!!! If algae is having that extreme an effect on your pH, it could also be robbing your system of dissolved oxygen overnight and your fish could suffer for it. So, if you do have an algae problem. Please do some pH tests at particular times of day to find out if your algae problem might be severe enough to kill your fish. Do a pH test just before dawn or as close to it as you can. If the algae problem is severe, the excess CO2 in the water will be acting as a mild acid and bringing your pH down. Then do another pH test in the late afternoon before dusk. Then compare the numbers. If the algae is causing there to be a drastic difference between your dawn pH and your late afternoon pH then it could be a big enough algae problem to endanger your fish for lack of dissolved oxygen early in the morning. Because like all plants, at night algae use Oxygen and give off CO2, they only give off Oxygen when it's light.

If the algae is a big problem, the cheap solution is usually complete shade for any tanks until the problem subsides. UV also works.
Do people use UV systems to clean out the algae? I had the opportunity to buy a brand new system for a bargain, but I passed it up because I couldn't imagine using it.

As for the algae... If the algae are a major problem, then your pH will increase throughout the day. How much is a drastic increase due to algae?

Could you also use a fine filter (ie, sand) to get rid of the algae?

Lastly, is there some place that consicely describes a lot of water chemistry problems associated with aquaponics? I have a textbook on Recirculating Aquaculture, but of course it is is pretty dense.

Thanks,
David
The Basic Info and Useful Info sections of the forum over on Back Yard Aquaponics is a fairly good resource on that though most of it isn't too deep into the chemistry, geared mostly for Backyard hobby people.
http://backyardaquaponics.com/forum/index.php?sid=a8a555031c041a078...
Thanks. That will almost certainly be good enough for me for now, although I am tempted to set up a large system and try to make some money with this down the road if I enjoy the smaller system.

I have the AP bug pretty bad right now, as you can probably tell by how often I am responding to posts. Right now I am sitting at my kitchen table sketching out my system... trying to figure out how to build the grow beds, what the relative water elevations will be, and how many cinder blocks I need beneath each unit to keep it from sinking into our sticky black soil.

David
I have read in several posts about people using oyster shells in their systems to stabilize the systems ph and to add minerals. Do the shells add or lower the ph? Our ph straight out of the tap is 8.0 and in my pond it can get up to 9.0. I have added spagnum peat moss to help lower, which is a trick when I used to raise wild Discus fish in the early 80's. It is helping some, but not a lot. I would love to hear more about the oyster shells, especially how many you need in a system. Might be worth going to get a couple of dozen for dinner!
Oyster shells are a calcium carbonate type buffer that will keep pH from dropping too low. Basically they tend to help keep pH above 7.6. They DO NOT lower pH.

FYI, I have attempted to lower pH in a system that is really strongly buffered to 7.6, it doesn't work. You might lower the pH temporarily but as long as some of the buffer remains, it will dissolve some more and raise the pH back up.

Jeff, do you have any rocks or concrete or plaster or anything that might affect the pH in your pond? I expect that if you were to aerate your tap water in a bucket for a day and then test the pH again, you will find that the tap water has a pH even closer to 9. What is your source water, well water?

A heavily loaded bio-filter can compete a bit with high pH media but only to an extent. I've seen my AP system get down as low as 7 when there was a heavy load of fish and the feed rate was high but now that the temps are cooler, the pH is back up.
Thanks for your help TC. We live out in the desert in So. California. All of our water is either pumped from a giant underground aquifer, but most of it comes from what they call the American Canal, which is basically the Colorado River. Most of these canals are lined with concrete. And, the water from the aquifer is also very high in ph. So, I am doomed with high ph. I just tested this morning after a long period of not testing and the spagnum peat moss is working. It is down around 7.5. I learned this trick from the old days of raising an Amazonian fish in aquariums. The only drawback is that it makes the water a little brown. When doing it in the aquarium I put a biofilter on the back of the tank and instead of having media I would just keep stuffing the peat moss in there, but it has to be spagnum. Back then it was long and stringy, now days it is ground up so I have to put it in fine material so it doesn't make a mess in the pond. I also have in the house a 135 gallon aquarium and I have the opposite problem with that. My ph in there runs between 6.5 and 7.0 and I use the same water. The difference is that in the aquarium I have 2 huge pieces of drift wood that help soften the water. The rocks in the bottom of the pond are river rock of the granite persuasion. I do have red sandstone in the waterfall that only runs about 2 hours a day. I know that is not helping, but not hurting a lot. I will change that in time.

TCLynx said:
Oyster shells are a calcium carbonate type buffer that will keep pH from dropping too low. Basically they tend to help keep pH above 7.6. They DO NOT lower pH.

FYI, I have attempted to lower pH in a system that is really strongly buffered to 7.6, it doesn't work. You might lower the pH temporarily but as long as some of the buffer remains, it will dissolve some more and raise the pH back up.

Jeff, do you have any rocks or concrete or plaster or anything that might affect the pH in your pond? I expect that if you were to aerate your tap water in a bucket for a day and then test the pH again, you will find that the tap water has a pH even closer to 9. What is your source water, well water?

A heavily loaded bio-filter can compete a bit with high pH media but only to an extent. I've seen my AP system get down as low as 7 when there was a heavy load of fish and the feed rate was high but now that the temps are cooler, the pH is back up.
Well, as you get enough plants to use up nutrients and allow you to avoid water changes, it should help a bit more to bring the pH down as long as there are no pH buffering materials in the system. I've found that I can adjust change out water prior to putting it in my system so as not to raise my pH above that of it's natural state (my limestone aquifer well water has a pH of around 8 once aired out) My system stable pH is 7.6 due to the shells in the media. I can use acid to bring the well water down to 7.6 and keep it all stable there.
some folks manipulate thier pH (down) using barley straw and artificial bogs, or by increasing feeding rates like TC said. oh, and barley straw is also effective at controlling algae, one drawback though is that you will end up with tannic water (just like you have now using sphagnum moss). with carbonate it's all or nothing- it is a great buffer because it precip.s out at a pH threshold (a little high for most prod.) and dissolves in quantities relative to dropping pH, (temp. dependent) so if you have enough of it and don't do anything too crazy, your water will always stay between your precipitation point and your total dissolution point (pH wise). so you know nothing will ever swing TOO far out of control. the problem is keeping nutrients soluble. i'll load a rough approximation of nutrient availability vs. pH when i have the chance.

Jeff Givan said:
Thanks for your help TC. We live out in the desert in So. California. All of our water is either pumped from a giant underground aquifer, but most of it comes from what they call the American Canal, which is basically the Colorado River. Most of these canals are lined with concrete. And, the water from the aquifer is also very high in ph. So, I am doomed with high ph. I just tested this morning after a long period of not testing and the spagnum peat moss is working. It is down around 7.5. I learned this trick from the old days of raising an Amazonian fish in aquariums. The only drawback is that it makes the water a little brown. When doing it in the aquarium I put a biofilter on the back of the tank and instead of having media I would just keep stuffing the peat moss in there, but it has to be spagnum. Back then it was long and stringy, now days it is ground up so I have to put it in fine material so it doesn't make a mess in the pond. I also have in the house a 135 gallon aquarium and I have the opposite problem with that. My ph in there runs between 6.5 and 7.0 and I use the same water. The difference is that in the aquarium I have 2 huge pieces of drift wood that help soften the water. The rocks in the bottom of the pond are river rock of the granite persuasion. I do have red sandstone in the waterfall that only runs about 2 hours a day. I know that is not helping, but not hurting a lot. I will change that in time.

TCLynx said:
Oyster shells are a calcium carbonate type buffer that will keep pH from dropping too low. Basically they tend to help keep pH above 7.6. They DO NOT lower pH.

FYI, I have attempted to lower pH in a system that is really strongly buffered to 7.6, it doesn't work. You might lower the pH temporarily but as long as some of the buffer remains, it will dissolve some more and raise the pH back up.

Jeff, do you have any rocks or concrete or plaster or anything that might affect the pH in your pond? I expect that if you were to aerate your tap water in a bucket for a day and then test the pH again, you will find that the tap water has a pH even closer to 9. What is your source water, well water?

A heavily loaded bio-filter can compete a bit with high pH media but only to an extent. I've seen my AP system get down as low as 7 when there was a heavy load of fish and the feed rate was high but now that the temps are cooler, the pH is back up.

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