I have a freshwater fish tank, and i need to lower the kh, how do I go about this?

Answer 1

Liszie and G have it pretty much covered here. If you are looking to LOWER the KH distilled water. But this cannot be done all at one time.

This is going to sound dumb but what kind of gravel do you have? Believe it or not certain types of gravel will keep your ph from increasing or increase it too much.

The property of water to resist changes in pH is known as buffering capacity. You can determine the capacity of your buffering system by measuring total hardness. A reading of 4-6 dH or higher is usually adequate to keep the buffering system in place and maintain a stable pH. A reading under 4 dH means there isn't enough of a buffering system and the pH is likely to drop. For higher pH levels, you will probably want to aim for 6-12 dH. Many hobbyists choose to measure only Carbonate Hardness (KH), which is a measure of the calcium carbonates in your water. This test is also effective in maintaining a proper buffer system. When testing for Carbonate Hardness, a reading of 75-100 mg/L is adequate for most aquariums, while a reading of 100-200 mg/L would be desired for higher pH levels. For the purpose of freshwater aquariums, measuring either total hardness or carbonate hardness is necessary, but measuring both independently would not be needed.

You need to know that anywhere in your aquarium where detritus (a fancy term for dirt) accumulates is a source of Phosphate production. As detritus accumulates in your gravel bed and on your filter pads, the Phosphate levels in your aquarium rise. Free Phosphate ions may bond with calcareous buffering material, precipitating calcium from your aquarium, and reducing your aquariums ability to keep pH stable. This is why it is so very important to clean your filter pads regularly and vacuum the aquarium gravel with each water change. In addition, your tap water contains buffering ions. Doing regular partial water changes will help to replenish the buffers which have been lost. This is important in all aquariums, because fish respiration and organic wastes alone will cause a gradual drop in the ability of your aquarium to buffer against pH swings.

Now the question becomes what to do if the fish you want to keep have very special pH requirements. If your fish prefer a pH level which is reasonably close to the pH your aquarium water is naturally buffered to, then I do not recommend you make any changes at all. Unless you are keeping an extremely specialized fish your fish will be fine. On the other hand, if your fish have pH requirements which are far from the values in your tank, then you have work to do.

Let us consider methods of raising the pH of your tap water. There are many additives on the market today which claim to raise your pH. Most of the liquid products on the market today are a 50/50 success at best when used alone only to find the ph will soon return to the normal level of 6. You also need to use a product to increase the buffering ability of your aquarium. To maintain a stable pH in the upper levels of the pH scale for fishkeeping, I would recommend using a buffering substrate such as crushed coral. You can add crushed coral to your existing aquarium. You can place larger amounts of shells or chrushed coral beneath the substraight in the tank. I personally place the crushed coral in a mesh bag and place the bag in my filter. You will want about 1 kg of crushed coral per 40 liters of water to buffer the water to hold a pH around 7.6. This method does not allow for the use of large quantities of crushed coral, but can be effective if you only need to make small adjustments to your aquariums buffering ability. This is why ocean items such as shells and ocean sand should not be used in a fresh water aquarium. It does raise the PH level.

Be assured that attempting to control pH is the most frustrating experience for a fish hobbyist. I would guess that 50% of the problems encountered in new aquariums are a result of the aquarist attempting to change the pH level. Few fish keepers actually need to adjust their pH. For the majority of aquarists your tap water pH will be adequate. The dangers of adjusting the pH incorrectly far outweigh any benefit you may receive by moving your pH a few points on the scale.

Remember, when it comes to adjusting your pH, less is more! Stability is most important. Routine maintenance is the key to keeping your pH stable and your fish healthy!

You can use distilled water as part of your water change little by little. Remember every time you do a water change you will need to replace the distilled water. (Not something I would suggest)

Answer 2

I agree with everything Gahpy said, but I'd like to add a few things.
First, you should know why you don't need to lower KH. KH is Carbonate Hardness, a rather technical term for buffer. I've also heard it called "alkalinity", but this is a misnomer. The amount of buffer in the water simply tells how stable the pH is, and the term alkalinity comes from the fact that "alkalinity" is a measure of how much acid can be added to the water before the pH begins to drop. Tanks with a higher KH are more stable and less at risk for pH swings and other bad things. You should be glad you have high KH (unless you WANT to change your pH, but that's another story)...
I believe you may be thinking of General Hardness (GH) which is a measure of all the dissolved minerals in the water, rather than just CO3, and can limit you in your fish choices. Pertaining to GH, water may be called soft, hard, or in between. pH is also tied into the equation, and soft water is usually acid, wheras hard water is generally alkaline. There have been cases where this is not true- my tap water is soft and alkaline. In my case, my GH is almost exactly the same as my KH, which means there is a lot of carbonate (and nothing else) in my water which makes it very stable, but also very alkaline.
For beginners especially, changing GH and pH is a risky proposition in the best of times. If your KH is too low, you take the chance of messing your water up big time, and if it's too high you could sit there pouring HCl into the tank until you're blue in the face and absolutely nothing would happen. (<-not recommended!)
Distilled water is soft and acid, if that's what your going for, but it is expensive compared to tap and you can't use it the way you would tap. Some of the minerals etc in tap water are needed by the fish, and just using distilled water would not be a good thing. Your LFS probably carries bottles of trace elements made for use with distilled water that would fix this problem, but once again, there is the expense side of it.
A cheaper idea would be just to accept your water the way it is. With a little extra acclimation time, most aquarium fish will adapt to in water up to 8.0 pH (relatively hard), but if your water is even more alkaline and harder, you will need to keep only fish that hail from, and thus thrive in, these conditions, such as African Cichlids and livebearers.
Good luck!

Liszie

Answer 3

I change 50% of the water in each of my three tanks every week. My water is 8.2 ph and 15 degrees kh out of the tap. I add 5g of RODI water for every 15g of tap water to lower the kh safely. A water softener won't do anything to lower kh or gh, it just replaces the minerals in the water with sodium, so the TDS remains the same. Go here for more info: www.plantedtank.net/forums

Answer 4

KH is Carbonate hardness and it's not very safe to start trying to lower. The result by using temporary patches like store bought liquids and chemicals is unstable water, which is much worse then values a little high.

The KH doesn't directly affect the livestock anyway - the bigger question is regarding your PH - a high kh often, but not always, results in higher PH and this is what effects the fish more directly.

If you really want to lower any values in your water, the only true reliable method is to remove the causes altogether through reverse osmosis filtration, or by buying distilled water. These types of water are lacking in the nutrients and minerals fish need, but if you mix it with tap water you can achieve the desired parameters.

In the end though, most fish are very tolerant of parameters and the whole thing is only worth messing with if you have very delicate fish or horribly hard and alkaline water.

Answer 5

Quoting Lizsie" cheaper idea would be just to accept your water the way it is. With a little extra acclimation time, most aquarium fish will adapt to in water up to 8.0 pH (relatively hard), but if your water is even more alkaline and harder, you will need to keep only fish that hail from, and thus thrive in, these conditions, such as African Cichlids and live bearers.
Good luck!"

That's a very good point! If you start messing around with water chemistry then it's an ongoing ordeal. I personally used to breed angel fish here in Austin TX. Water out of the tap here is 7.8PH and I was dropping it to 5.6-6 PH. Trust me you don't want to start that route in messing with your water conditions. Staying constantly is important with fish aquariums. Once you adjust the fish to the faucet water you're fine from then on. However that goes to say that keep with the above quoted. Don't keep African's if your PH out of the tap is 6.5 and certainly don't keep Discus at 7.8PH levels. Just using that as an example.

www.txholeyrocks.com

Answer 6

Ditto Ghapy

MM

Answer 7

Amen, Ghapy! Nothing to add to that!

Answer 8

what is kh???!!!!!!