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Discussion Starter #1
I have a 55 gallon tank, and i realized the pH is kind of high- 8.9.

Before using peat moss, I was going to try adding stone to bring down the pH. If it doesn't work satisfactorily, then I'll resort to the peat moss.
 

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With so high pH you probably have high KH too. You need to bring the KH down first. Easiest way is to mix RO water with tap water during water changes to get reasonable parameters.
You can choose fish that will thrive in your hard water too and never worry about adjusting parameters.
 

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Good morning, i never saw a rock which lower acidity if someone find some i am interested to know.

Michel.
 

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Those I can think of are pretty much inert or have carbonates which tend to raise rather than lower PH. Peat is the more common method, so I think it may be true that there are no rocks to do it.
But then, it is true that there are lots of things I've not heard about!
 

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Discussion Starter #8
With so high pH you probably have high KH too. You need to bring the KH down first. Easiest way is to mix RO water with tap water during water changes to get reasonable parameters.
You can choose fish that will thrive in your hard water too and never worry about adjusting parameters.
i use RO water. but i think the problem is the contents of the tank, not the water source. the water's pH was neutral.

in the tank i have an undergravel filter powered by a powerhead. i think it does something to the water (probably raises pH)

if the new layer of acidic rock (or peat, if i can't find a suitable stone) has water go through it, i'm hoping the tank's pH will go down.
 

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What KH has the water you are adding to the tank? What KH has the tank water itself?
If something rises pH in the tank you need to find it and get rid of it, easy as that. It probably is gravel or some kind of rock. Switch out decorations and substrate and problem should be solved.
Acidic rocks exist, but it only means they won't make your water harder. Peat moss helps only if KH is low enough, it gives weak organic acids.
 

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Discussion Starter #12
i don't know the KH... i need to get a new test kit. the rocks in the substrate is white pumice stone. there's some dirt in the rocks, but i recently replaced all the stones. the undergravel filter pulls water through this, and then back into the tank. if acidic rocks aren't an option, i guess i should proceed with the peat moss.
 

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I was not familiar with pumice stone for aquariums, so did some reading and now I might have some real questions of their value for this purpose. Is this something that you have used before without trouble or a new item? I find one of the uses for pumice is making concrete blocks and that says very alkaline to me.
I might think that the pumice is the problem and other subs would work better. Trying to get the PH down while using a highly alkaline sub would not be one I would want.
But that may be due to my lack of experience with pumice! It's volcanic and I tend to stay away from volcanic types as there is no real way to say what was melted and left in them.
 

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But that may be due to my lack of experience with pumice! It's volcanic and I tend to stay away from volcanic types as there is no real way to say what was melted and left in them.
Pumice usually forms from high-silica lava that is low in calcium and magnesium. Chemically, it's perfectly safe for a tank, unless lime has been deposited by groundwater in its pores. You can test by putting a little strong acid on it and seeing if it bubbles. You can also get rid of any lime residues by soaking it long enough in a strong acid.

True pumice is actually light enough to float on water because of the many pore spaces. If what you have sinks easily in water, it's more likely scoria, but the distinction is not that important -- it, too, will be no problem for water chemistry unless groundwater has deposited lime in its pores.
 

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I have seen a PH that higher in the past. PH was 9 just before the lights turned off. But just before the lights turned on the PH was about 7. This repeated daily I was able to solve the problem by simply dimming the light. Let me know if that works for you. I was not using CO2 at the time.

I concluded that my new brighter light was enough to get the plants to start consuming carbonates in the water. For example plants consume the carbon from calcium carbonate, The calcium then reacts with the water to for calcium hydroxide which is a strong base and will increase PH. When the lights were off CO2 levels in the tank increased increased allowing the calcium hydroxide to convert to Calcium carbonate.Calcium carbonate dissolved in water pushes the ph to about 7.

I do not know of any acidic rocks. But I have also observed PH dropping when using a sulfate based GH booster. Seachem equilibrium and nilocg gh booster are made from a mix of calcium sulfate and magnesium sulfate. Plants need a lot of calcium and magnesium but very little sulfur So when plants are growing well the plant consumption of Ca and Mg may result in an increase in sulfate levels. Sulfte in water is acidic.
 

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Surf this happens but uncommon. In tanks with high lights, no co2 injection and fast growing plants. Elodea is quite known to be able to produce the calcium decalcification. Google this term "biogenic decalcification".

CO2 injection solves this issue, lowering the lights level (or duration), adding KH (buffer/carbonates), with Seachem Alkaline Buffer for example.

Michel.
 

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I was not familiar with pumice stone for aquariums, so did some reading and now I might have some real questions of their value for this purpose. Is this something that you have used before without trouble or a new item? I find one of the uses for pumice is making concrete blocks and that says very alkaline to me.
I might think that the pumice is the problem and other subs would work better. Trying to get the PH down while using a highly alkaline sub would not be one I would want.
But that may be due to my lack of experience with pumice! It's volcanic and I tend to stay away from volcanic types as there is no real way to say what was melted and left in them.
I've never heard of anyone having issues with pumice or other volcanic rock in an aquarium. One of the more common use for pumice is in the aquarium for biomedia. I have bags of it in my canister filter.
 

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I too have never heard of slow dissolving acidifying rocks that don't leach heavy metals / want to push the pH ridiculously low. Like iron sulfide (pyrite). I'm suggesting that you should never use this btw...
 

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Discussion Starter #19
I do have CO2, but i've been using a powerhead to dissolve the gas, so I haven't turned it up. I ordered a CO2 reactor. but i wonder if CO2 will make more than a marginal difference.

I don't have many plants in the tank yet. just some hygrophilia, anacharis, and a few baby mangrove trees. oh, but there is a massive root structure from the pothos plants i have growing out of the tank. maybe the roots are doing that to the water?



maybe a 1/3 of the pothos roots in this tank:


and a pic of the white pumice:


aside from a few mosquito fish and a few snails, there isn't much else in the tank. except perhaps beneficial bacteria.

i froze some peat moss and placed it under the substrate, next to the undergravel filter. it made the water brownish, but it didn't affect the pH.

i was thinking of removing all the substrate from the tank and replacing it with activated carbon topped by clay balls. but that's assuming the substrate is the problem.
 

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Discussion Starter #20


So, i dunno if it's the CO2 reactor i added (and upped the CO2 being released by the regulator) or the peat moss, but now the tank's pH is down to 7.4. i think that's promising.

i learned that calcined montmorillonite clay has the properties i wanted in a stone that lowered pH- in another thread, someone showed me the secret:

https://www.plantedtank.net/forums/...l-filter-substrate-activated-carbon-clay.html
 
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