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Discussion Starter · #1 ·
I'd appreciate members' thoughts on this.

I received my Milwaukee MC122 pH meter to control the timing of CO2 injections. Standardizing the meter at 4 and 7 was easy.

Then, I placed the probe in the tank and got a pH reading of 8.0! Quite a difference from the 7.4 I get with API Aquarium Kit and 6.8 with the Tetra strips.

Rechecked the probe this morning thinking I made a mistake calibrating the Milwaukee. But again it reported 7.0 using the calibration fluid. Putting the probe back in the tank resulted in pH 8 again.

I realize the Tetra and API kits require some interpretation, but the color is spot on with the API kit, and a reasonable interpolation for the Tetra stick test. More importantly, my wife confirmed the readings.

I'm shocked at the range of readings. Fish are doing fine. Plants are not great, which is why I'm injecting CO2. Temp is 80.
 

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If your pH probe is reading the calibration solution correctly, I’d say it is an accurate reading for your tank.
 

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Discussion Starter · #5 · (Edited)
Yes. That's what I'm thinking.

Taking it a step further, what does that say about the other readings we get from the kits? If ammonia is 0, is it really?

They teach doctors, you don't treat the number, you treat the patient.
 

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Put your PH probe in the tankard leave it there and then check it 5 hours later. Some PH probes are slow to respond to PH changes. Others may be faster but you probably bay more for them. Your liquid test kit however will report the correct PH in less than a minute.

Note the PH of your tank water is not entirely dependent on CO2. Calcium, Magnesium, sulfur, chlorine, and potassium will all have much stronger effect on PH than CO2. Also having the lights on and off also can have a strong influence PH. If I measure the PH in the morning and then just before the lights turn off the difference between the two readings is currently about 0.5. If I brighten the lights a little bit the difference will be very close to 1. IN my experience CO2 is probably not the cause of your plant growth issues. It is more likely that you have a nutrient deficiency. possibly from insufficient calcium, magnesium, sulfur, chloride, or zinc or iron. These deficiencies are much more likely than a CO2 deficiency.
 

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Discussion Starter · #8 ·
I just checked the pH about 2 hours after the lights turned off in a dark room, and it reads 7.7.

Are you saying that I need to use a liquid fertilizer? I use the grow tabs, but have been inconsistent at dosing Flourish.
 

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Check your pH before the CO2 starts up. Then check again maybe 4-5 hours in. That should be most CO2 saturation.
Then use this formula to roughly guess how much CO2 is in the water

CO2ppm = 3 * 10^(pH2-pH1)
 

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I just checked the pH about 2 hours after the lights turned off in a dark room, and it reads 7.7.
Leave the PH probe in the tank for the next 24 hours. and check it periodically. You need to know the morning (lights off) PH and the PH at lights on PH just before lights off. and it wouldn't hurt to gather several PH measurements during the day.

Are you saying that I need to use a liquid fertilizer?
No I am saying you need to verify all 14 nutrients are pressent in your fertilizer and Tap water. The14 nutrients plants need is nitrogen, potassium, Calcium, Magnesium, phosphate, sulfur, chloride, Iron, Manganese, boron, zinc, copper, molybdenum, and nickel. If just one of these nutrients is not pressent plant goth will slow and then stop and eventually the plant may die.

For example if you look at many fertilizers you will find most don't have calcium. The few that do don't have enough. There are 2 reasons for this. Calcium when mixed with the other fertilizer ingredient doesn't dissolve. So many fertilizers leave it out because it is often pressent in tap water. Socheck the GH (general hardness of your water source. The GH test only detects calcium and magnesium. if your GH is zero you don't have any calcium and magnesium (softened water or RO water will have a zero GH reading. TheGH test generates a number in degrees orPPM (parts per million or miligrams per liter). Many people like to see a GH of 3 to 6 degrees or 53 to about 100ppm. If it is low you can use a GH booster such as seachem equilibrium to increase the GH.

Flourish comprehensive does have calcium and magnesium in the ingredients list but there is only about 1 ppm of both present in a tank dosed according to the instructions on the bottle. Flourish comprehensive is a rather strange fertilizer, based on the level of nf nutrients in it it was apparently designed with the assumption that your tap water has about 70% of the nutrients needed. Which is unlikely for most people. i guess they assume you have too many fish in your tank.

You should also look at the ingredients in root tabs. Some root tabs only have about 4 ingredients. I don't use root tabs because you cannot predict how fast they dissolve and as a result you cannot predict what the PPM levels will be in the water. However I do know of one person that has had good results with flourish root tabs and flourish comprehensive in his tanks.

You can also look at the leaves of your plants. if they don't look right that may help you identify the nutrient deficiency. Sites like this one may then help you identify the issue.

also look at your water test results if you measure zero nitrate that is not good. I keep my nitrate at a minimum of 5ppm.

It is also important to dose fertilizers consistently and to do a water change once a week in the tank. I do a 50% water change once a week and dose fertilizers at that time.
 
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