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Discussion Starter · #1 ·
I am new to planted tanks but not to aquariums as my wife and I have multiple tanks ranging up to a 135 gallon Lake Malawi cichlid tank. I have just set up an 80 gallon planted tank that will house rainbows. I have a problem in getting the water chemistry correct for the fish and plants. The tank is set up with flourite as the substrate and has a pH controlled CO2 system and a substrate heater.

I have added plants but not yet started to add the fish because the tank pH is 5.9. This is confirmed not only on the pH monitor but also by testing using an Aquarium Pharmaceuticals test kit (pH 6 as that is as low as it tests.) The KH is 2 Dkh and the GH is 3. The tap supply is pH 7 with a KH of 2 and a GH of 2. I have been told to avoid at all costs phosphate buffers and would like some suggestions with how to raise the pH to around 6.8 and the procedure for raising it. Needless to say at this pH level the CO2 system will not engage. Also the tank has 260 watts of compact florescent lighting. Your help with the pH and any other suggestions are most appreciated.
 

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Hi,

To have optimal plant growth you need to have 30 ppm CO2. Provided that your substarate is inert (I think fluorite is) and your KH=2 then you should shoot for PH=6.4. If you PH is below that then you need to decrease the co2 injection. In order to aclimate the rainbows you might want to shoot for even lower CO2 level - say 20 ppm (PH = ~6.5).

And above all - have fun - here's a rainbow in my tank...



Aviel.
 

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If your pH is 7.0 out of the tap, and 5.9 in the tank, there must be something in the tank driving it down. Do you have any things like different rocks, ornaments or driftwood in there that could be the culprit?
 

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Discussion Starter · #4 ·
Thanks for the replies and the suggestions. I do believe that the culprit is 4 large pieces of Malaysian driftwood releasing organic material. I talked to Seachem today and their suggestion is to add Alkaline buffer along with Equilibrium to raise the GH and KH along with the pH. I appreciate the input as to pH and CO2 targets. I also realize the the hardness numbers are related to pH but can someone give me a good idea as to a target for the hardness numbers. This will give me a starting point to monitor so I can determine the levels to maintain. I also assume that I need to monitor these closely to determine when the driftwood will start to cease leaching. I would like to be able to start adding fish this weekend, your opinions, please.

Thanks in advance.

colem
 

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aviel said:
Hi,

And above all - have fun - here's a rainbow in my tank...

Aviel.
Aviel
What are the red plants and the greenish/red tipped plants in the back? I have not seen those before. Thanks
 

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I'm using just plain baking soda for buffering. It appears to me that the Seachem Alkaline buffer is essentially the same thing as baking soda; their FAQ states that it is a "sodium bicarbonate-based buffer". That's baking soda, so you can just use that if you want to save some cash.

Baking soda/Seachem alkaline buffer will raise both pH and KH. If you have a higher KH, then the acid/base equilibrium system will be more "buffered" and hence the pH will be more stable with CO2 injection (ie, drop less). If you add more, you can inject the full recommended amount of CO2 without driving your pH too low.
 

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I agree with the above--I would either add buffers (which is a pain, IMO), ditch the wood for something more nuetral, or keep a species of rainbow that is more attune to those parameters (probably something from New Guinea).

Here is the single best resource for rainbowfish to be found on the web, just in case you haven't seen it already: http://members.optushome.com.au/chelmon/Contents.htm
 

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I agree with the previous posts - using buffers makes for a never ending chemistry experiment. I'd check out the CO2 system first as the most likely culprit. Try reducing the bubble rate in half and measure the impact on Ph. Also make sure its off at night. If not,then I'd check the wood. You can try removing the wood or testing a sample of it. If you want to keep it there are several ways to try to neutralize its impact on Ph.
 

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Discussion Starter · #9 ·
Update on Rainbow tank

Just as an update and for further information in case someone has an interest.

First of all the pH readings were taken at a time when the CO2 system had only been test run for about 20 minutes total and had not run at all for 2 days prior to the test. Therefore, I do not think that th CO2 was the cause of the low pH. I talked to the manager at the aquarium store where driftwood was purchased and she told me that they have other customers that experienced a lowered pH but that they have told her that the wood will stop leaching after about 3 months. The tank is already planted (with moss attached to some of the wood) and I would have to start over not to mention the fact that my wife really likes the wood so I guess I will have to do some diligent testing to keep the water chemistry correct until the wood neutralizes. I have buffered the water with Seachem Alkalinity buffer (3 applications, one day apart of 3 3/4 teaspoons each for the first 2 applications and 1 tablespoon the 3rd day.) I also added one application of Seachem equilibrium at the recomended dosage which I do not remember at this time and do not have my tank log with me.) The numbers are now pH 7.0, KH and GH are both 5 without the CO2 running.

The CO2 system is controlled by a Milwaukee SMS 122 controller that I now have set to cut off at pH 6.7. Does anyone have an idea if this is about the right setting. Thanks in advance.
 

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Using Bicarbonate to increase KH isn't nearly as frightful as a lot of folks think. Once you figure out how much it takes to increase your entire tank to the level you want it's just a matter of dividing that amount by the percentage of water you're changing. ie 5 tbsp/100g= 5KH If I do a 50% WC then I know I have to replace 2.5tbsp to maintain 5 KH, it's as easy as dosing KNO3. :)

As for your particular case colem, with KH of 5 and a pH of 6.8 you'll have 23ppm CO2, which is plenty for all but the highest light tanks. At ~3.2wpg 23ppm is just fine. If you feel you need more, drop the pH Controller to 6.7 NO LOWER. Just keep in mind that the higher the CO2 the higher the metabolism of the tank and the easier it is to get algae. Your lighting will support that metabolism, but limiting it with lower, but sufficient CO2 will keep things a bit more forgiving.

Best,
Phil
 
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