question on PH and KH - The Planted Tank Forum
 
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post #1 of 9 (permalink) Old 09-12-2009, 11:21 AM Thread Starter
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Question question on PH and KH

I have a somewhat planned 55g with about 2W/g and I also have well water which comes out of the ground at about a ph of 5.9. I use a calcium carbonate injection pump system to being that up to about 7.0. I do a 25% water change every two weeks, even before the change all my params are 0 nitrate, nitrite, ammonia, KH is about 60 ph is 7.4. After the water change ph is 7.4. So the question is why is the ph high? are the plans using all of the CO2 making the PH go up? Should I use the water before its buffered? Is the acid water do to dissolved CO2, could I be that lucky? I use flouris excel.
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post #2 of 9 (permalink) Old 09-12-2009, 02:57 PM
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Well water very often contains a lot of dissolved CO2. That would cause the low pH. You can easily check this by letting a shallow container of fresh well water sit out in the air for day, stirring it up a few times, to allow the CO2 in the water to dissipate. The pH will rise if the low pH was due to CO2.

Why are you changing 25% of the tank water every two weeks? You can do fine just adding water to replenish evaporation in a low light tank. Since you use Excel it isn't hurting anything to do the water changes, but they aren't really necessary that often.

A pH of 7.4 is far from being high. It is just about as normal as you can get. And, adding calcium carbonate isn't necessary either, unless you have very low GH, which means low calcium in the water. Plants do need calcium and magnesium, so a low GH should be corrected with a GH booster, such as Flourish Equilibrium.

Also, you say you have 2 watts per gallon on that 55 gallon tank. If those 110 watts are from a couple of T5HO lights, you have high light intensity. If they are from 4 T8 lights, without reflectors, you do have low light. If they are from 2 55 watt AH Supply kits, you have high light. Saying you have 2 watts per gallon doesn't tell us much.

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post #3 of 9 (permalink) Old 09-12-2009, 09:31 PM Thread Starter
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Ok, I have been looking for a way to test for CO2 directly but that is a good test I will try the CO2 test you describe.
Several books I have read indicate that water changes are good even if params are all good because they introduce essential nutrients and minerals. So I do a 20% every 2 weeks. How often should I do water changes?
The calcium carbonate injection is done for the domestic water supply and not just for the aquarium. The water was so acidic that it was dissolving the copper in the pipes. Plastic piping is now required by code, in out township, due to the acidic well water. I could snag the water for the aquarium before it goes into the calcium carbonate injection system.
I have a 48” USA Current sattellitefor lighting


thanks for the reply
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post #4 of 9 (permalink) Old 09-12-2009, 10:57 PM
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As long as you continue to use Excel, dosed as recommended on the botttle, you can change water as often as you like. The Excel will maintain the available carbon above the needs of the plants, so the fluctuations caused by water changes shouldn't cause algae blooms.

I don't have any data for the Current Sattelite light fixtures, so I'm not sure if that gives you a low enough light intensity to consider the tank to be low light. If those were AH Supply 55 watt lights, with their reflectors, you would have too much light to treat the tank as a low light tank. I doubt that the Current reflectors are as efficient as the AH Supply ones, so you may be ok there.

It will be interesting to find out what happens to the pH of your tap water after it sits out in the open, outgassing any CO2 in it for a day. Since the calcium carbonate is able to increase the pH as it does, that suggests that the water does have a high amount of CO2 in it in the water pipes.

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post #5 of 9 (permalink) Old 09-15-2009, 03:32 PM
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How did the degassing test of the tap water go? I'm dying of curiosity here.

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post #6 of 9 (permalink) Old 09-16-2009, 11:40 AM Thread Starter
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Thumbs up update on the water

Sorry but I was in Cleveland visiting my brother when I started this thread. Ok, last night about 9:00 I put water in a shallow tray from the untreated side of the water conditioner. The PH read 6.0 but that is the bottom of my current test kit. With previous kits I have see it as low as 5.7. At 7:00 the next morning I saw lots of dissolved gas on the surface of the container. I took another PH reading at to my amazement it was 7.2! Making the assumption that the low pH is due to very large amounts of dissolved CO2, follow my logic here, why can't I inject my untreated ground water as a source of CO2? being the DIY kind of engineer that I am I am always looking for a project.

thanks for taking the time...
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post #7 of 9 (permalink) Old 09-16-2009, 03:13 PM
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CO2 dissolves very readily into water, but it also "outgasses" very readily. So, an open container of water will always be dissolving CO2 from the atmosphere and losing it back to the atmosphere at the same rate. When we diffuse CO2 into our aquariums most of that CO2 soon escapes back to the atmosphere, so to maintain a high concentration of CO2 in the water we have to continuously diffuse more CO2 into the water.

If you relied on the high CO2 content of the ground water for CO2 in your aquarium you would have to have a continuous flow of ground water into the tank, with an overflow to avoid overfilling the tank. As a guess I would expect to need around 100 gallons per hour for that flow for a tank that size, in order to maintain something near 20-30 ppm of CO2. I'm basing this on the fact that when we use a DIY external reactor in our filter return line we are running about that much flow, and that flow may have about the amount of CO2 dissolved in it as your ground water.

Brief answer - it would work, but it would waste enormous amounts of water.

EDIT: After a bit more thinking, for a low light tank, a little bit of CO2 could be enough. So, if you were trying to get something closer to 10 ppm than our usual 30 ppm, you wouldn't need as much water flow. And, that suggests an interesting test that could be done. Use a pH probe to measure the tank water pH. Then collect data on tank pH vs. groundwater flow through the tank. Finally, use a drop checker to get a one point "calibration" of tank pH vs. ppm of CO2 in the water. With that you could determine what water flow rate would maintain the tank at 10 ppm, or 5 ppm, or whatever you wanted to shoot for.

But, suppose the concentration of CO2 in the ground water is seasonal? Oh well........

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post #8 of 9 (permalink) Old 09-16-2009, 05:34 PM Thread Starter
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thanks....
I have a 10g in the basement that I use for temporary storage of plants, kind of like a nursery. I think I am going to try and play around to see what if any changes I can make to the PH with continuous water changes. Just as an experiment. I will post my results. It will be a week or two before I have any data. I may drill the tank. or better yet build a new acrylic tank. I have a few extra 1/2" and 3/4" sheets laying about, just might bite the bullet and practice for building my new 60"x25"x16~100g [ would go where an old wet bar was ]
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post #9 of 9 (permalink) Old 09-16-2009, 09:49 PM
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Sajata, when you do this please report the results in one of the other forums, this one would be best, http://www.plantedtank.net/forums/fe...er-parameters/ so a lot of people who will be interested can see it. Not everyone follows the low tech forum. I will be watching for it.

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