# how does pH down work?



## Wei (Jan 1, 2005)

Current tap is too high and even with injected co2 im only able to get it down to about 7.6. Im looking for a way to lower my pH and ran across pH down. Does it have any ill effect I should know about?


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## KevinC (May 24, 2004)

If you get a high enough CO2 level (depends on KH as well as pH), you don't need to use a pH down product. However:

I'm not sure if you are referring to one particular product, so I'll talk about reducing pH in general:

Some pH down products use phosphoric acid (H3PO4) or monobasic sodium phosphate (NaH2PO4). Both are acidic (pH<7) and will lower your pH. The problem is the resulting phosphate available for algae growth. The acid reacts with bicarbonate and carbonate ions in the water, ultimately producing water, CO2, and phosphate.

Other pH down products use a dilute mineral acid solution (HCl or H2SO4). The resulting chloride and sulfate ions will not cause a problem in the tank. Here the acid also reacts with bicarbonate and carbonate ions, producing water, CO2, and the chloride or sulfate ions. 

One other warning though: these products work by destroying some of your bicarbonate buffering (KH). If you are injecting CO2 as well, you could end up with a pH crash. Also, be sure to re-measure KH after using these products BEFORE you turn the CO2 on.

Kevin


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## malkore (Nov 3, 2003)

DO NOT USE PH DOWN!

this is a temporary chemical 'fix' that won't last long at all. Best way to lower pH is to use CO2 injection, or cut your tap water with RO water.

Why do you think pH down is a solution? and why do you think your pH is too high? 7.6 is a fine pH for 99% of fish out there. If CO2 injection won't lower it, pH down might, but it won't increase your CO2 levels. As soon as you start adding acids or artificial buffers to the water, the pH/Kh chart goes out the window because the chemistry isn't natural anymore.


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## Hypancistrus (Oct 28, 2004)

If your tap has a high pH due to a high kH, then Seachem Acid Buffer will lower the kH and therefore the pH. It will not invalidate the CO2 chart.

I don't know what is in pH Down, so I can't recommend it.


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## DarkCobra (Jun 22, 2004)

I have used a pH Down product in the past before I started CO2 supplementation, and I can tell you that it was pure algae in a bottle.

It was phosphate-based, but it didn't say that on the bottle. Only in very fine print, "Not for use in planted aquaria." It didn't go into the gory details of why: "...because it will smother your plants in algae!"

Don't use a pH reducer unless you're *certain* it's not phosphate based. Hydrochloric and sulphuric acid based products are fine. Common pool hydrochloric (muriatic) works and is $6 for a lifetime supply, but you have to dilute heavily it prior to use. It's far too dangerous to handle in the original concentration. Be careful doing that.

But if your water has such a high KH that you need a pH reducer in addition to CO2, you may want to look into using distilled or RO water instead.


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## tazcrash69 (Sep 27, 2005)

If you need to lower your pH, you could supplement tap with RO water.
It's a lot more natural that pH down.


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## TAF CAF (Jan 12, 2006)

I have used PH DOWN several times, as my water is very high pH and I prefer to keep 7.0 (for breeding and sensitive fish). I have found that using it causes no imediate ill effects, but for long after I have hell with keeping the pH balanced. 

I try to use *distilled* water from the store pre mixed with my tap water to more naturally lower the pH.


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## Wei (Jan 1, 2005)

thanks guys I think I will take ur advice and stay away form it and just slow bump up my co2 injection til I get the right pH.


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## malkore (Nov 3, 2003)

One thing to note: if you're lowering pH to get fish to breed, CO2 may not work at all to induce spawning.
Fish 'feel' both the pH and the hardness of the water. It seems that its really the hardness that induces spawning not pH alone.


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