A lot has been written regarding the influence of kH on pH, pH swings and the deadly PH crash, but it can be very complicating to figure out for some what it all actually means.

So in this article we will explain in basic layman’s terms about the relevance of it all.

The Basics
Let’s start with the pH of your water.

You are looking at water from your tap, after all this is the only way to fill or top-up your pond. Depending on your location, the water supplied to your home will have a different pH level, with some areas maybe at 7 whilst others could be 6.5.

This is the starting point for all koi keepers, unless you are going to use water from a different supply completely which most of us don’t do i.e. a natural spring, or well system, and if this was the case the same principle would apply.

Firstly, what’s your tap water pH?

The easiest way to check this is with a dedicated pH meter, rather than a pH test kit as it’s more accurate and sensitive when measuring Ph values.

Here’s a quick explanation: pH test kits usually measure pH in increments of ones, like a pH 7 or pH 8 or maybe somewhere in between. Someone may say after testing pond water “my Ph readings were between ph7 and ph8″ which is more of a difference than you may think.

The pH scale is Logarithmic, meaning that each 1 measure is 10 times more acidic or alkaline depending on which way its going (up is alkaline, down is acidity and Ph 7 is neutral).

So if your pH was 7 and went up-to 8 it would be 10 times more alkaline, not just 1 unit more – and if it when up to 9 from 7 it would be 100 times more alkaline.

Some Examples
Here are a couple of examples of ponds that need a bit of help in achieving the correct balances:

The first pond is 2500 gallons that was filled with tap water with a pH of 7 (neutral – middle of the scale) normally once a pond matures the pH can move around a bit normally.

So in this instance, after 6-12 months (which should be long enough for the pond to be fully matured) the pH is 7.6, and regular weekly checks confirm this to be consistent…

…the key to pH reading is consistency. So as long as it does not move around too much (it’s called a swing) everything would be fine, moving of say 0.6 would be acceptable, and pH can differ dependant on what time of day you take your reading, morning or evening time, but within these tolerances would be more than acceptable.

If you were doing regular water changes, for filter cleaning or top ups, then the water you would be replacing would be from the tap at a pH of 7 as long as you weren’t changing large amounts of water the impact on your pond would be minimal, and still keep you within the 0.6 tolerances levels.

You can also measure the KH reading in your tap water.

KH is the level of carbonates in the water which enable it to buffer the Ph, which is like the blood supply for the pH, and without it the pH is in danger of swings and a possible crash.

A simple test is available to test your kH levels and guides to what are the best levels, but the starting point is always to test your tap water kH first to find out what your starting point is.

The measurements of kH is in either dH or PPM – if you are using the dH scale 6 and above is favourable. Lower than 50 PPM is dangerous, due to kH being depleted daily in your pond by all living organisms.

pH Crashes
So what is a pH crash?

It’s when your pH levels drop dangerously low (below 6.5) would be considered a crash, with the most serious cases causing total fish loss.

Unfortunately we needed to get a bit more technical to explain why things like pH crashes happen, and why we have to buffer pH or kH levels in our ponds.

The next pond example we will use is again 2500 gallons, but with a lower tap water pH of Ph 6.8.

Once matured, after the same 6/12month period, the pH settles out at 7, but the kH is only 1 on the dH scale, with the tap water kH readings no higher than this.

The problem now is when you are changing water in the pond filter or top-up fills, the only thing that’s keeping the pH level around the 7 mark is the tap water itself, with no support from the kH in terms of carbonates to buffer the ph.

If regular water changes aren’t continued in the winter months when we don’t tend to do much water changing then due to the lack of carbonates being produced, the life support of the pH is in danger of dropping to levels that may cause a pH crash.

This is where you can help with the kH problem if it’s too low.

Buffering can be done to raise the kH to more of stable level by adding bicarbonate of soda (baking soda) at a dose of 1/4 cup per 1000 gallons.

This will also raise the pH levels, so slowly raise the levels over a period of days.

Note: baking soda will only take your pH to a maximum of 8.5 – and not above – no matter how much you put in. Introducing it will help to replenish the heart beat of the pH and give stability to both kH and pH.

What’s your ph? Is it consistent or does it swing?

If it’s where it needs to be and your kH is supporting your pH and both have acceptable levels, you don’t need to do anything other than keep an eye on them.

The pH side of pond keeping is really boring because most of the time you check it and it’s the same results time and time again…

…boring but correct which is the important thing.

kH Levels
Your kH reading will tell you before your pH reading will when you are about to have a problem.

This is due to kH levels starting to drop which will then start to affect the pH but will give you enough time to react and do something about it before the deadly pH crash happens.

If your kH levels are between the required levels (above 6), it is very unlikely that you will have a pH crash even if your pond is at 6.5 – this is because there is enough carbonate to support this pH and not allow it to drop any lower.

This is why kH is a very important part of water testing.

Normally we have a least 2 customers per year that suffer from a pH crash, and most lose all or most of their fish.

One in particular has had this happen twice over the past 4/5 years with each time being in winter.

The last time his pH had dropped to 5, it hadn’t happened in the summer months due to water changes, but in the winter when he stopped changing water causing the lack of carbonates and an already low-ish pH of 6.8 causing the pH to crash and kill all his fish.

Since then, he has buffered the pH and kH up to recommended levels and monitors this more in the winter months and again the first check will be kH.

Any signs that this is being depleted then baking soda will be added to buffer, and the problem will be overted.

Key Takeaways
Firstly, don’t panic! There may not be any issues with your pond’s pH or kH levels, but as above this only happened twice in 5 years and both times he’s lost a lot of fish.

So check to ensure your reading for kH and pH are where they need to be, and if not make some adjustments as described above and hopefully you don’t suffer the same problem.

Don’t let the kH become too complicated – think about it as the heart beat and blood supply for your pH and without it there is a good chance your pH won’t work correctly.

pH Crash Cheatsheet
pH levels – Recommend 6.5 -8.5 Better (7.5-8-0) 7 is neutral (below 7 acidity – above 7 Alkalinity)

kH levels (dH or PPM) – Recommend 4-16dH Better (7-10dH)

Raising Levels (Ph-KH) – Bicarbonate of soda (baking soda) 1/4 cup per 1000 gallons and/or oyster shells in the filter.