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I have a 300gal 96in L x 30in W x 24in H. In the tank i have a big stump, a log, and a few sticks and twigs. Substrate mostly sand, some crushed coral, river rocks. Before i put all this wood in my pH was always around 7.6 now it has dropped to 6.8. what is the best way to get the pH back up to 7.6 area? also have a little crushed coral in the sump. I was thinking about adding more coral in the sump, will this buffer the ph to basic? Or what can i add to buffer it to 7.6ish?
Thanks Jason

Hi

Many things will buffer the PH and bring it up to the point you want.
To be honest the PH will start to go back as the tannins from the bog wood are removed due to your weekly water changes.

pH 6.8 is fine for most fish, so I'm not sure why you want to change it...

Obviously, as macsvog says, the pH will rise again when the majority of tannins have been removed with the water changes...

If you need to buffer the water, bicarbonate of soda in small amounts - measure your KH (which is a measure of the buffering capacity) - if it's below 2 dKH (about 36 ppm), the water is unstable and pH will fall dramatically.

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Mats

thanks! I want a higher pH for central american c******s, otherwise I would be fine with 6.8. Also i was alittle worried that water changes are temperarally raising the pH since my tap water has a higher pH. So i want to make sure the pH is stable. What kinda time frame will it take to remove all the tanins? its been two months.

Hi

A lot longer than 2 months.

May I sugest you take the wood out and soak in running water?

If you make BIGGER water changes, you will:
1. Remove more tannin each time.
2. Raise the pH because there is more buffering capacity in your tap-water, so more "new" water in each change, will raise your starting pH before the water change.

Since you want hard, alkaline water, you may also want to add calciferous rock in the tank. Texas Holey rock for example.

I spend most of my time trying to get my pH lower...

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Mats

The easiest way to lock pH to 7.5 - 7.7 is to put some limestone or chalk in the aquarium. Just add them and forget; it can not be overdosed, will not raise pH above 7.7.

A more complicated way is to use bicarbonate. Bicarbonate can raise pH to 8.3, so if you want a pH lower than that you need to monitor pH while adding bicarbonate, or balance the pH by adding CO2. This is a temporary solution, the pH of the aquarium will slowly drift back down by releasing CO2 to the atmosphere, so you will have to keep monitoring the pH and adding bicarbonate as needed.

Much the same goes for adding sodium hydroxide, only more so, and I do not recommend using it.

There are also commercial buffers available. There's a wide variety of possible buffer combinations which will give you that pH, and it's hard to generalize about them. They work, but may or may not have unintended effects.

Another very real possibility is that it's not your water but your pH test kit that's changed. Test kits age rapidly, and you might want to double-check the pH before doing anything, definitely before any use of hydroxide.

Mostly the best thing to do when it comes to water chemistry in the aquarium is nothing, but if you really need to raise pH my advise would be to buy or collect some limestones and add that.

Hi

This may be very slightly off topic so please move it if you wish Mods.

The whole subject of water and its chemical composition is raised by this post.
I am not a technician when it comes to water. I did spend around 20 years trying to get water that had some similarity to the water I was getting my fish from, for 19 of those 20 years I thought Ph was the key I thought if I got the Ph to 6.5 I would be able to keep and breed any south American catfish and never have unexplained deaths.
I used resins, water softeners, plants, bog wood you name it I brought it.
Then I found a Kh kit and it all slotted in to place.
Water needs some form of Kh.
I now use RO and HMA mixed to give me a Kh of 5 to 7 and a TDS of 170 to 210.
I do daily water changes with this water and a weekly water changes with neat cool RO. I then let the tank stand with no feeding or water changes for a week.
I am now keeping and spawning fish I would never have dreamed of attempting to keep at one time.

I think it's fine to continue discussing various water related chemistry/components of pH-balance in this thread.

And yes, KH is one way to achieve stable pH. In natural water, KH is the most common stabilizer of pH - so in natural water, low KH -> low pH, high KH -> higher pH (up to around 8 - which is about as far as we want to reach in an aquarium). KH is not the ONLY possible buffer, however, and a KH test won't show up for example a phosphate buffer. But phosphate buffers are rare in natural water.

The other interesting point is that, at least from what I know about the subject, pH isn't very important to fish. Conductivity is the important factor. Conductivity is the measure of how well the water conducts electricity, and it's also what an eletronic TDS meter measures. Low conductivity, in nature, usually means low KH -> low pH.

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Mats

KH in aquaristics is really alkalinity. This mix-up is caused by the fact that in most natural waters alkalinity and KH can be assumed to be the same thing.

Alkalinity is the ability of the water to resist pH change, the "buffering capacity" of the water. In most natural waters the buffering is done by bicarbonate and carbonic acid in equilibrium with the atmosphere, while commercial buffers are often based on phosphates.

Distilled (or RO) water has almost zero alkalinity, and pH will therefore vary wildly at the addition of even tiny amounts of pH raising or lowering chemicals. Extremes of pH and rapid fluctuations are unlikely to be healthy for the fish, so I would assume that adding buffer to get a reasonable alkalinity is a good idea.

I tried to find out howcome natural waters with very low conductivity, such as the ones many tropical fish come from, still manage to have relatively stable pH. As far as I can tell they are buffered mainly by a complex mix of organic acids, notably tannins, which take over from carbonate buffering when the pH is lower than 6.5.

EDIT: I would agree with Mats that conductivity is a more important parameter than pH.

Of course, conductivity, when we're talking about most natural waters, will also reflect the KH indirectly because if the conductivity is low, the KH is also, by itself low. So, as a rule, we can say: low conductivity = low KH = low pH. High conductivity = high KH = pH around 7.5-8.

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Mats

MatsP wrote:as a rule, we can say: low conductivity = low KH = low pH. High conductivity = high KH = pH around 7.5-8.

Normally, yes. It is possible to get high conductivity and low alkalinity or pH (for instance by adding table salt to distilled water) but in nature conductivity and alkalinity are normally correlated.

Absolutely agree. And there are also the possibility of alkaline substances, sodium hydroxide for example, being in the water, which would make the water have high pH, and not very high conductivity. But again, it's unusual in natural water.

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Mats

This was a great read thanks

I would like to know when mixing the RO with HMA water at what ratio should they be mixed?
Instead of HMA water could you use regular treated tap water? Or is having a HMA device/filter better?

Thanks

If you have your own RO-unit, then you can mix RO-waste-water (which is essentially the same as HMA water, as both have passed through a carbon block filter, just slightly more concentrated). As to the proportions, you should use the proportion that gives you the right KH/GH/pH values.

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Mats