pH too low? - The Planted Tank Forum
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post #1 of 7 (permalink) Old 06-01-2009, 01:06 AM Thread Starter
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Question pH too low?

I've been trying my hand at planted tanks and am a bit confused over the pH changes I'm having.

I have 2.25wpg over 20gallons and keep microrasbora and otos, and 1.89wpg over 29gallons and keep danios and otos.

I have several types of plants and they grow well, some getting pink/red on the tops. They pearl a lot and I must trim once a week.

Everything seems healthy and stable. I've had only one fish death and it was my fault when doing a water change and accidently siphoned out a fish that later died.

I just started keeping readings on the tank with the test kit that measures the pH, ammonia, nitrite and nitrates. This is the API Master test kit.

My tapwater has ph of 8.8 (maybe higher, that's the highest the test kit measures), ammonia between 0 and 0.25, no nitrite or nitrate.

The 20gallon tank has pH of 6 (maybe lower, that's the lowest the test ket measures), ammonia and nitrite 0, nitrate between 10 and 15.

The 29gallon tank has pH of 7.6, ammonia and nitrite 0 and nitrate at 20.

Should I be concerned about the low pH of the smaller tank?

They've both been up and running for about 6 months now. Other than feeding the fish and doing 50% water changes, I've not added anything to either tank since they were set up.

Any advice or suggestions of what to do would be very helpful and thank you in advance.

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post #2 of 7 (permalink) Old 06-01-2009, 02:32 AM
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Do you have a single 55 watt PC bulb fixture on each tank? And, do they have large, highly polished aluminum reflectors? Are they right on top of the tanks? If so, you have too much light on both tanks to do without some fertilizing, including a source of carbon, either CO2 or Excel. Does the 20 gallon tank have any wood in it? That could lower the pH due to tannins. In any case 6.0 or even 5.5 is not too low a pH.

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post #3 of 7 (permalink) Old 06-01-2009, 06:36 AM Thread Starter
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I'm sorry I didn't give more information.

I have the Coralife fixtures with 55 watt bulbs (they have the reflectors), I forget the exact Kelvin, but it was 9000 or so. The 20gallon has one bulb, the 29 gallon has two bulbs, but I only use one (the one that uses the fan). I'll use both if/when I get pressurized CO2.

Both fixtures are on the plastic legs above the tank (3 inches above the water surface).

I use DIY CO2 for both and both have driftwood in the tanks. The driftwood does not change the water color at all (I boiled them and soaked them off and on for weeks before I started the tanks).

I currently use "Natural Aquarium Vital" every other day per the dose on the bottle.

I just purchased dry fertilizers to use once the Vital runs out, but the instructions on which to use or how often was not included. I have:

Plant Trace

I'm waiting for the instructions from the seller.

My concern is that since it is so low I do not know how low it really is since the test kit only shows 6 or more.

Someone at a LFS said to put baking soda in the water, but didn't know how much.
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post #4 of 7 (permalink) Old 06-01-2009, 03:05 PM
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It is highly unlikely that the pH is too low in that tank. Even if you use CO2 you can't drive the pH down low enough to be a problem for the fish. I suspect the wood in the tanks is the source of the lower pH in the one tank. And, while I'm not sure, I don't think tannins can drop the pH below acceptable levels for the fish. Remember, many fish naturally live in very brown stained water, just full of tannins from leaves, etc. Adding baking soda will raise the pH when it is CO2 driving down the pH, but one of our chemistry whizes will have to comment about whether it also raises the pH when it is tannins that are dropping the pH. If you want to try baking soda, adding a half teaspoon at a time, waiting an hour or so, measuring the pH, then adding another half teaspoon, as needed, should work fine. Just don't add a big amount all at once - sudden changes in KH are harmful to the fish. is some good information about how to dose those fertilizing chemicals you now have.

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post #5 of 7 (permalink) Old 06-01-2009, 04:20 PM
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1/8 tsp/6.65gallons of water = 1dKH
1/4 tsp/13.21g = 1dKH
1/2 tsp/26.42g = 1dKH so you can figure your volume from there.
Make your measurements with leveled teaspoons. Scraped flat to the spoon lip once filled with powder not heeping full.

2dKH usually tests as 6.8-7pH
3dKH = 7.2-7.4pH
pH readings are water w/o CO2 injected.

This should help if you want to raise pH.

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post #6 of 7 (permalink) Old 06-04-2009, 01:59 PM
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I am having the same problem with my 20g as well. My pH reads 6.0 (I know it is lower than that but cant locate a good test to detect it). I would like to get it higher and would like to know how without adding phosphates to buffer it up.

I dont have any Wood in there at all and it is my most planted tank. I dose Excel every other day as well as Trace. When those bottles get low I will replace with dry ferts.

The only decor I have in the tank is 3 granet rocks, but that is now going to lower the pH in the tank. My shimp tank has a pH of 6.1 to 6.3 in it at all times. The substrait in both tanks are the same as well as most of the plants. I do not dose the shrimp tank much because it is low light and does not require much TLC (plus I just dont care about the plants in that tank much).

I have 2 t-8 strips on the 20 and do a DIY CO2 at the moment. A Eheim 2213 and Rena X3 are hooked up to that tank as well, but that should not effect the pH of the water.

So again, how to get the pH up without melting all my plants?
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post #7 of 7 (permalink) Old 06-04-2009, 02:54 PM
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Adding ordinary Arm and Hammer baking soda, or a different brand, will raise the KH of the water, and that raises the pH if there is any CO2 at all in the water, which there always is. But, I don't know of any good reason to raise the pH. The pH of aquarium water is nothing more than a consequence of other things that generally aren't a problem for a planted tank, so worrying about pH isn't necessary or desirable. Making changes in the water, by adding things like baking soda can do a lot more harm than just not measuring pH. When you change the hardness of the water you need to do it slowly, not with one big addition of baking soda or other chemicals. Then, when you change the water, you have to be careful to match the water parameters as you change water. If you just use tap water, adding nothing except a dechlorinator it is much easier and easier on the fish and plants.

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