Tropical Fish Keeping - Aquarium fish care and resources

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dancexonxwater 04-20-2010 06:53 PM

Hardness & PH
So my local water has changed and the pH has become too high. The fish store gave me something to increase the GH because my pH won't stick. I put in enough to increase it 1DH today. But after I put it in, i didn't notice anything different on my KH test kit. In the kit it gives the same reading chart for kh/gh, so i figured they went hand in hand. Also, I was specifically given this kit to test the hardness.

I'm confused though, can anyone better explain this to me?

KSASTER2 04-20-2010 07:04 PM

My tap water was also very soft... it would come out over 8.0 and then over a few days in the tank drop below 5.0.

As a fix I bought some rock that is for saltwater tanks. It's limestone base rock they use for salwater tanks.
I added a few nice pieces and now my ph is a constant 7.2 been that way for months now.

dancexonxwater 04-20-2010 07:54 PM

If my Hardness increases, will my KH also increase?

Byron 04-21-2010 12:42 PM

GH and KH are obviously related, as is pH to both, but not equally so there can be variation depending upon several factors.

I have done my share of fiddling with pH and hardness over 20 years, so if you can provide some information I may have some suggestions. Adjusting hardness and pH can sometimes be problematical and with fish in the tank (presuming) this could be fatal.

The first thing is to find out what you have in terms of tap water pH and hardness and what you want to achieve in the aquarium in terms of pH and hardness. And what fish are/will be in the tank. Also, what is the product the store gave you?


dancexonxwater 04-21-2010 04:08 PM

In my tank I have one molly. the PH is about 7.6. and I would like it to be more like 7.2 so i can add other fish to the tank. I would like to add some guppies, most likely.

The KH test kit tells me that dKH is 53.7ppm. and the product i have to make the water harder is "Equilibrium " by Seachem. "restores & maintains mineral balance & GH"

Byron 04-21-2010 04:51 PM

Equilibrium I have used myself and it seems to work with no other issues, as far as I can find out. However, it does get expensive since obviously it has to be used with every water change [I no longer use it]. And in your situation, it actually is at cross purposes to what you want.

If the hardness test is accurate, a KH of 3 is soft, and this means the pH of the aquarium may slowly drop. This occurs in all tanks, where there is nothing to prevent the acidifying of the water which is due to the natural biological processes ongoing in the aquarium. My tap water has a pH of 7.0-7.2 but < 1 dKH and GH, and in my 70g and 90g the pH went down to 5 [I let it, it was not accidental]. I keep the pH in the 115g at 6.2 by using dolomite to buffer the water.

The pH of 7.6 is fine, ideal in fact for all livebearers. But it will probably lower gradually if you do nothing (assuming again the hardness test is accurate). But a change from 7.6 to 7.2 is minimal in terms of its effect on the fish, and in my view the guppies and molly will be fine at 7.6. Raising the hardness of the water will also likely increase the pH, the two are related, which is the opposite of your intention.

I would leave it as is, but monitor it regularly, at least once a week before the partial water change, and if any change in pH is evident, monitor it daily. Always test pH at the same time each day to obtain a more accurate reading, since the pH naturally fluctuates during the day and night especially if plants are in the tank; this is termed the diurnal cycle. It is possible the pH may lower continuously over time, and in that case with livebearers I would certainly take steps to buffer the water and keep the pH above 7. Dolomite or even crushed oral in the filter would achieve this at much less cost.

Hope this helps a bit.


dancexonxwater 04-21-2010 05:05 PM

Yeah that was really helpful, thank you. I'm probably going to leave my tank as is for now then, as you suggested.

But I'm just curious, if I did want to lower it in the future for different fish, for example Neons. Adding minerals wouldn't increasing the buffering capacity? What would?

Byron 04-21-2010 05:39 PM

Raising hardness normally also raises pH, and for soft water fish like neons you do not want this, unless you have extremely soft water like I do, then it is not so big an issue. If you wanted acidic water, you also want soft water. In terms of fish, those that prefer acidic water also require soft water since this is how it occurs in nature. Neons come from such waters, although most are commercially raised in harder water and it has been discussed among several of us the extent to which this applies; I don't want to enter that debate here. The issue is much more critical with wild-caught fish, like cardinals.

There are a few streams in South America where the pH is around 7.6 and the softness is still low. But the fish in those areas, and I have some of them in my Amazonian aquaria, do very well with lower pH because it is the hardness/softness that is actually more significant. I'm thinking of Mikrogeophagus altispinosus, the Bolivian Ram, which is found in waters having a pH of 7.6 and also in other streams with a pH between 5.5 and 6.5. This fish is clearly adaptable. But in both cases, the softness is less than 3-4 d GH with even less KH. In my 115g my male M. altispinosus is thriving at pH 6.0-6.4 (diurnal fluctuation).

Harder water means more dissolved calcium and magnesium, and this creates difficulties for many forest fish, such as calcium blockages of the kidneys. Provided the pH remains stable, which takes into account the diurnal fluctuation, the fish will manage well in soft water. Buffering the pH in soft water is relatively simple. I have done it for years using dolomite. This obviously raises the GH slightly, but it buffers the pH fairly steadily in my experience. My 115g has been at a pH of 6.0-6.2 and a GH of < 2 d for many years. This low degree of hardness seem to cause no problems for the wild fish. The 90g which has no dolomite runs at zero GH and a pH between 5 and 6 and the fish are all wild-caught from streams with zero hardness and a pH somewhere between 4 and 5 or slightly higher.

Now, some fish do have problems at lower pH. Nematobrycon palmeri (Emperor Tetra) show signs of real stress if the pH falls below 4.5 whereas the cardinal does not. So one does not want the pH to be out of control, hence the minimal amount of dolomite to maintain a GH of <1 which does prevent the pH from falling below around 6. The other thing of course is the biological filtration. Nitrifying bacteria basically die off at a pH much below 6, and some say below 6.5, but of course in well-planted aquaria this is somewhat irrelevant since the plants consume the ammonia. But it is an issue that has to be realized.


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