# Help with GH level



## Yokomo99 (Aug 26, 2008)

I just purchased a KH/GH test kit and used it on my 135 Gallon tank. The results were a KH level of 6 and a GH level of 12. I know that the GH level is high but the instructions are a little vague on what these levels mean and how to correct them. Any suggestions would be appreciated.

Matt


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## trenac (Jul 16, 2004)

GH will always be higher then your KH. I personally would not worry too much about it unless you are trying to keep a soft water fish. Here is a site with some good info on water chemistry... http://www.aquariaplants.com/waterchemistry.htm


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## Philosophos (Mar 1, 2009)

GH is the measurement of total mineral ions in your water. Fish aren't easily bothered by a slightly elevated GH, and it's hard to bother them or your plants with the parts of it that are not KH. It is in fact necessary to maintain a certain level of GH to keep osmotic pressure up in fish, and keep your plants fertilized.

KH is a convoluted hobby term for alkalinity, given that your test measures all alkalinity, and not just carbonate. One degree of KH, or GH equals about 17.9ppm. KH is often seen as part of GH, and is usually lower. Things like NaHCO3 can prove an exception to this rule. In practical terms though, I've never seen KH exceed GH in an aquarium. KH keeps your water buffered from acids (produced through the nitrification process) and roughly correlates with PH. For instance, I'm guessing your fish tank is sitting around 7.4-7.8 pH, unless you're running compressed CO2. Some plants like this level of pH, some don't. The same applies for fish.

So then, where does this leave you? I would say that if your 135g is still a work in progress, you have some choices to make. If you want an easy aquarium to take care of, buy plants that like slightly harder water, and don't demand much CO2 or light. This will not be the highest density or most diversely planted aquarium, but it can still be made to look good. Aquariums such as these tend to rely a bit more on their hardscape for pleasing visual lines. If you're new to planted aquariums and have little other experience is botany, this isn't a bad place to start.

On the other hand, if you don't mind learning or refreshing the first couple chapters of first year chemistry, and you and you've got a green thumb, there's the high tech methods. With compressed CO2 and a drop checker for monitoring, you could probably keep your pH down to neutral or a little below, without even having to effect your KH. This would be suitable for keeping the vast majority of fish and plants. With 30ppm CO2 comes the kind of upkeep that requires some serious dedication. You'll need high lights, high current, regular ferts, etc. to keep everything balanced.

Of course there are points in between these two. Where you want to land is dependent on your own level of knowledge, and the time you want to dedicate to the aquarium. 

-Philosophos


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## Yokomo99 (Aug 26, 2008)

Thanks for the answers. My PH is 6.8, KH is 6 and the GH is 12. I just checked my tap water and it has a GH of 10 and the KH is 6. My tank has pressurized CO2 and 220 watts of T5 lighting. Is it necessary to lower the GH to make it suitable for most plants and if so can I use distilled water to lower the GH?


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## Philosophos (Mar 1, 2009)

6.8ph? Sounds like you've got your CO2 tweaked nicely. The lighting looks good too based on what I've heard for T5's and mmols.

Unless you're trying to induce spawn and have viable eggs for heckel discus and appistos, I wouldn't worry about your parameters. Your plants need any of that GH that isn't KH. I use 100% RO water and modify the chemistry to purposely reach 2KH, 6-7GH. The KH is low because I want water that can give viable appisto eggs. Without the GH as high as the aforementioned levels, most plants and fish would start to suffer. From there, the limited nutrient base of magnesium and calcium would slow plant growth, and then cause a phosphate or other nutrient imbalance followed by an algae bloom of a species depending on the excess that occurs. 

If you're wanting to do really soft water for sensitive fish and plants, then 50% RO/DI water would make a great blend. This is because of the need to reduce KH rather than the permanent hardness portion of GH. I notice that your GH is higher in the aquarium than out of the tap, so I'm assuming that you're using fertilisers? 50/50 tap water/RO should look like 3KH/6GH, then fertilizers (at the rate I'm seeing here) will bring it up to 3KH/7-8GH, and a reduction to 6.5pH. This is a rough estimation of course, but in my opinion, that's near-perfect water. If you want to go 100% RO water, I can give you my current methods/opinions, but things get a little more tricky.

-Philosophos


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