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Does Texas Holey Rock leech sufficiently into a more acidic water column to steadily buffer the ph..?

- If CO2 was running with this rock - with the CO2 lowering the water's ph - would the rock react against the acidic water, leeching carbonate etc and keeping the ph steady while CO2 levels were increasing? Making it nigh impossible to calculate the CO2 levels in the water..?

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Pretty much. Texas Holey Rock is just limestone. It's actually just trash rock from a limestone quarry near my parents house just north of Austin, TX. It will definately buffer the pH and increase the alkalinity of the water.

The C02 might overpower the rock a bit... But it will keep your water from going horribly acidic over time... Texas holey rock is a somewhat slow acting...

Ok, thanks for those replies.. I'm running CO2 and suspect that the rock is affecting the ph/co2 readings. I didn't think it was that reactive, but only one way to find out - take it out!

It also depends on how hard or soft your water is, as well. If your water is very hard an already high in other desolved minerals, the rock will not "desolve" as quickly, but if your water is very soft, like from an RO unit, it will "desolve" or leach into the water quicker.

The same thing will happen with calcium based items in your tank, such as Aragonite, and sea shells. They will break down quicker in soft water than they will in hard water. I have had sea shells, completely desolve in about 6 months in RO water.

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There is always a bigger fish...

- That was my query regarding the CO2 making the water more acidic. On the last tank there was a slight ph drop with the CO2, whilst there being no texas rock - this tank's ph hasn't budged. The water from the tap is moderately hard with a ph of around 7.5-7.8.

Well that is a good thing, if it is buffering the ph to hold, when the CO2 levels are higher. Have you taken any readings several hours after the lights are out, or a couple of hours before the lights are on? As this is when your CO2 levels will be higher, and thus can cause the more significant drop in ph. I would be interested to know how much difference you have in that tank with the holey rock. I would also be interested in the difference in your other tank, at the same time, for comparison. Makes me think about doing some experimentation with my planted tanks. hmmmmm.....

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There is always a bigger fish...

Well I tested the ph early in the morning, then last thing at night, when the plants are pearling and the co2 has been running all day - they measured the same.

I'm unable to do running comparatives with the other setup, as the tanks were swapped round and the smaller setup has been upgraded to the 4' setup.

Only thing I can think of is if the co2 mix is insufficient for the 30 odd gallons of water? But the smaller tank was a very similar volume, give or take 5 gallons.

However have removed the rock and will retest in a day or so to see if any difference has been made.

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The reason I ask about testing at night when the lights are off, is because the CO2 levels are higher, as the plants use O2, and release CO2, thus increasing the CO2 levels when added to the CO2 injection you are using. This can cause the ph to drop. My interest is, how well the holey rock, limestone, ect, helps to buffer the waters capacity to hold the ph up, and not let it drop at night.

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There is always a bigger fish...

I tested this morning before the lights came on, and according to the chart, there was 12ppm CO2, which is dropping to 3/4ppm by the end of the day.

Would you recommend adding an additional CO2 mix? Don't think I have *very* fast growers in there - theres mainly Amazon Sword, a smaller type of Sword, crypts, some Wisteria, and a little Val.

(This may be better moved to Planted?)

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I have been contemplating moving it to planted, but was waiting to see what direction is took.

Did you happen to check the ph at the same time as you took those higher CO2 levels?

As far as adding more CO2, are you adding ferts. The additional CO2 will not get used, if the plants don't have additional ferts to use at the same time. Also, I don't know your lighting levels, but you many need to increase the lighting as well, but you may have enough too, lol. The point is, the plants need all three things to live and thrive, light, ferts, and CO2. When you start increasing one, you also need to increase the other two for the plants to make use of them. Other wise, it is just a waste.

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There is always a bigger fish...

The CO2 calculation was done from the ph value with KH.

- I might add some more CO2 then, as there is ample ferts if not too much as algae is (not taking over) but in the tank. Theres about 2+wpg light.

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