View Full Version : How to raise KH

12-12-2002, 1:34 AM
OK...here's what I have...

29g community unplanted tank

Ammonia~ 0ppm
Nitrite~ 0ppm
GH~ 125ppm
KH< 17 ppm
PH measured at 6.4

What would be the best way to raise KH to keep the PH more stable and perhaps a bit higher (we'd like to have a pH of 7) without adding a bunch of chemicals? Our tap water measures KH at < 17ppm and pH of 7.

Is there one particular item we can use to buffer for a pH of 7 but not raise our GH?

I'm sorry if this doesn't make much sense...I think I am confusing myself also...

Thanks in advance

12-12-2002, 1:35 AM
Add crushed coral but that will raise ph too,kh and ph usually work hand in hand.

12-12-2002, 1:36 AM
like how much will it raise it? and how much should i add?

12-12-2002, 1:38 AM
i know that the higher the kh usually the higher the ph...and a really low kh can mean ph shifts, and a lowered pH

12-12-2002, 2:02 AM
Don't worry,i assure you people with more knowledge about ph and related issues will answer your question.I know little about ph and related,all i know is kh is carbonate hardness,hard to achieve high kh with plants since plants take in carbon

12-12-2002, 2:39 AM

hi, i think this might help.....


12-12-2002, 5:30 AM
Cheapest and fastest way would be to use Baking Soda.

Use a 5g bucket ... fill it with your tap water. Then conduct some experiments on the 5g bucket w/ Baking Soda to see how it alters your KH and pH. Apply what was learned from the 5g bucket to your tanks volume.

12-12-2002, 8:58 AM
I've never found baking soda to have very lasting effects, at least not when used by itself.

In low KH situations, it is correct that a strong increase in KH can drive up pH. The trick is to boost KH just enough to provide buffering (resistance against pH change) while not raising pH any more than absolutely necessary.

I would recommend you get some crushed coral. You won't need much- a cup at max, I would think. Start by putting a tablespoon or two in filter bag (a clean nylon stocking would work, too). After tying off the bag, place it in your filter. As the coral slowly dissolves, KH will gradually rise. This can take a week or two, so don't expect anything overnight. You'll need to monitor pH and KH. When KH reaches some more satisfactory level -- say, 100 ppm -- you might want to remove a bit of the coral from the filter bag, unless the KH creep has leveled off. If KH stabilizes before getting to 100 ppm after a couple weeks, add another tablespoon to the bag.

This method produces a very slow increase in KH that will have minimal impact on pH. Even if your KH drops when you do partial water changes, it will creep back up before the effects of bioacidification can drive down pH.

Good luck,

12-12-2002, 9:19 AM
What is wrong with chemicals? That is the easiest way to do it. I use Seachem Cichlid buffer. It buffers the ph to 7.0. As far as hardness is concerned it should level out as your ph levels out. IME acidic water is usually soft and alkaline water is harder. Good Luck. :)

12-12-2002, 12:05 PM
Why use chemicals when you can do it naturally.....Crushed coral is a natural, much more permanent solution to the KH/PH problem.
Many of us have found that in matters pertaining to PH, when we've used chemicals of any kind the PH bounced all over the place.
Try about 1/2 tbsp of crushed coral. If your results tell you to add a LITTLE more, add until you achieve the results you're looking for.

12-12-2002, 12:15 PM
I just went through this same experience with my PH lowering in my 72 gallon tank. I considered chemicals but I didn't know what else they might do to the tank water. Besides crushed coral is way cheaper and easier to use. I just put a cup into a perf bag into my Fluval and eventually it stabled out at 7.4. You know that the water is going to be mixed properly that way. Next filter change I will remove about half of it I think. Better to start slow like DJ says maybe a tablespoon at first.

12-12-2002, 12:51 PM
Thanks everyone....I guess I just missed all the threads with this good advice!

Fishmaster~ I just want to keep the chemical usage to a minimum...somethings might have affects that I don't know about and would rather just stay away from them. I'm no expert. And crushed coral seems like a better, longer term solution to buffering. :)

12-12-2002, 2:40 PM
I'm not sure where all the references to "chemicals" are coming from. I think there might be some misconceptions floating around.

Buffers and Baking Soda are essentially Sodium Carbonate or Sodium Bicarbonate. They are not chemicals.

Ask yourself what KH measures .... it measures Carbonate Hardness.

Crushed Coral is simply carbonate based, thus as it dissolves it increases the carbonate hardness. Baking soda .. crushed coral .. both carbonate based.

Whichever road you take to increase your KH, it all boils down to the level of carbonate in your water. Be it Baking Soda or be it Aragonite Sand or Limestone rock .... etc.

It can take a while for crushed coral to dissolve and get the desired affect. Even still, depending on your tank's volume a cup or two here may not be enough. Of course it depends how high you want to raise your KH. But certainly a 1/2 tbsp of crushed coral will do absolutely jack for your water. Personally, I think crushed coral does a better job of buffering when used as a substrate vice a cup or two here and there.

I honestly believe the test on a 5g bucket is worth the shot. You'll notice that w/ Baking Soda the results are immediate and contrary to what has been said, it does last a long time. I use it in all my AFrican tanks.

Now take another 5g bucket and put a cup of crushed coral in it.

You can then compare the results for yourself.

Don't get me wrong, there is no right or wrong here. Its just a matter of different methods .. so don't think I'm flaming those "crushed coral" fans ;) However, Baking Soda is super cheap and is not a chemical. I prefer it over crushed coral because it acts quicker. In the end, they both raise Carbonate Hardness (KH) .. I just tend to feel one does it faster than the other.

AS for Cichlid Buffers .... those are just well packaged containers of Baking Soda. If you are using things like "AFrican Cichlid Buffer" and want to save money then don't use it anymore. Instead go buy yourself a few containers of Baking Soda. I purchased 10 pounds of baking soda for about $4. I think a small container of Cichlid buffer costs about $6. Talk about Saving money ;)

12-12-2002, 3:00 PM
I've used Seachem's Malawi/Victoria Buffer in the past, and it took my pH considerably higher than baking soda ever did...

I'm no chemist (maybe one will jump in here and educate us!), but it seems quite possible that certain substances (e.g., carbonates vs. bicarbonates, sodium bicarbonate vs. calcium carbonate) would have differing buffering capacities.


12-12-2002, 3:20 PM
Well I don't use my chemicals that often. I actually read the instructions. I use it once per week or every other week depending on what happens. I don't use ph up and down because yes the ph will bounce all over the place. I use a buffer and it works great. I never knew you could use coral in a filter. I haven't been back into the hobby long enought to learn all that I have forgotten and learn new things but I am trying! :) I don't like to use to many chemicals either and yes they are expensive. To each his own is what I always say.

12-12-2002, 3:27 PM
JS ...

I agree, there are more mixes of carbonate .. bi carbs .. etc in the Pre-mixed buffers. Whereas, baking soda is just the Sodium bicarbonate.

Even considering that, I still think the baking soda gets the pH/KH high enough. Especially for Rift Lake tanks.

I just can't bring myself to paying their prices compared to DIY ... etc.

I've tried coral in the canister .. but could never get it over 7 KH. Which is what led me to the baking soda thing.

Fortunately we have several ways to skin a cat in this whacky hobby ;)

Not a chemist either ;)

Home Depot sells a really inexspensive coral based sand. They sell it as South Down. That would be great for buffering your water as well .. especially as a substrate. I think it looks a bit better than crushed coral.

P.S. another trick for making your water harder ... if you want to raise GH .. you can use Epsom Salt ;)

12-12-2002, 4:16 PM
I've resorted to making my own Rift Lake salts/buffer solution. I use epsom salts, sodium bicarbonate, and some form of other carbonates. I formerly used Corallifes Carbonate Hardness Controller, but I don't think it's sold any more. I now use Aragmilk. I get good buffering, a bit of a pH boost from my tap water's 7.8, and it's WAY cheaper than the commercial preparations.

In my Rift Lake tanks, I shoot for a pH of 8.0 or so, KH of 240-280 ppm and GH of about 350-400 ppm.


12-12-2002, 5:21 PM
I had a kh related problem. I wanted to do a new tank with pressurized co2. A kh of 4 or above is a good idea to have to help prevent ph crashes. While my tap is ph7.4/gh6/kh5, over time the kh tends to drift down towards 2-3.

To prevent this from being a problem I experimented with crushed coral in my 45 where the kh had dropped. I started w/ 1/4 cup in the filter and eventually raised it to 1/2 cup. I was able to get the kh up to 5 without raising the ph so I decided this was the solution for the new co2 added tank, a 50 gallon.

The 50 is filtered with an Eheim ProII 2026 whch has a bag of crushed coral in it. I usually put a fresh 1/2 cup in every few months. The params in the 50 ph7.2/gh6/hk6.

My feeling is smaller amounts of crushed coral in the filter will raise kh and barely effect ph. However larger quantities, especially when used as a substrate, will definately raise ph as well. The only problem I had was I could not find a bag of crushed coral smaller than 25lbs. So I now have a lifetime supply as far as kh needs go.