Pond pH

Why does it fluctuate?

The pH of your pond water fluctuates depending on the time of day you test your water. Testing your koi pond water in the morning for pH will give you a lower pH reading than testing pond water in the afternoon. The KH or "carbon hardness" of your pond water is one factor that will determine just how much your pH will fluctuate within 24 hours. Every pond is unique and no two ponds are exactly the same. pH readings for your pond could range from 7.6 to 8.1 or 7.1 to 7.5 or even a bigger range between the high and low pH may occur. This is the unique daily pH cycle of your pond. One word of caution: don't fall into the false   belief that your pond water must stay below a certain pH reading, here's why.  

You're going to have a natural pH high in the late afternoon, this is normal. The very worst thing you could do is panic, because according to what you read your pH must be kept, lets just say below 7.5 and yours is 8.2. Now you want to add a chemical to bring your pH down, which is an acid.

WRONG! By adding the acid you just shocked your koifish by interfering with the natural pH cycle of your pond! Sudden pH changes (especially lowering the pH) will stress your koifish which can lower their resistance to bacterial infections. Plus, adding the acid to lower your pH in the afternoon could cause an overnight "pH crash" which will kill your koifish. Yes, you could have a pond full of dead koifish in the morning!

Here's the reason why: Because it is natural for your koi pond water to have a much lower pH at night and the addition of the acid will cause your nighttime pH to drop to dangerous levels. Your koifish have adapted to the natural slow pH cycle (up and down) of your pond water and it does not stress them.

What causes the natural pH swings in my pond? No tech talk! 

During the day plants and free floating algae in your koi pond produce oxygen and take up carbon dioxide CO2. The decrease in CO2 increases the pH in your pond, caused by photosynthesis (sunlight on plants). At night the plants and algae take up oxygen and produce CO2 which decreases the pH in your pond. That's why your tests show a low ph and low oxygen level in your pond water early in the morning.  Plus, all the bacteria, your koifish and the sludge on the bottom of your pond all have an effect on the oxygen and CO2 levels of your koi pond. O xygen levels in your pond? That's another article.    

How can I prevent a deadly pH crash in my pond?  

There are the two life supporting elements in your Koi pond that can be related to your home.

A home without a solid foundation will fall. The pH in your  Koi  pond will fall without a solid foundation of carbonates (KH)  carbonate hardness . Good  koi care means keeping the (KH) at a safe level in your koi  pond. A KH reading above 140 or better.
 

A fall in the pH of your  koi pond   stresses your  koi and if low enough can even kill them. pH is measured on a scale of 1 to 14. A reading of 7 is neutral, below 7 your water is "Acid" above 7 your water is "Alkaline". A good reading for   a koi pond is 7.5 or better. Koi and the good bacteria in your filter thrive in alkaline pond water.
 

The carbonates (KH) in your   koi   pond determine how stable your pH is. Your  koifish  and the bad and good bacteria need and use up the carbonates in your  koi fish pond everyday. Without a good carbonate base in your water, your pH will fall below 7 and your water will be in the "Acid" range.   I   don't believe in lowering the pH in an aged koifish pond with a ZERO ammonia reading unless the pH is very high (9 or above).
 

You can raise  your  pH in your koifish  pond   very quickly if you see a "pH crash" coming, without hurting your  koi fish, however, if you try to lower your pH and it drops even two points   within a few hours, your koifish can become VERY stressed and could even die. note: A high pH in a  koifish pond with a high ammonia reading can be a   very serious problem , because ammonia is more toxic with a high pH. I still would not drop the pH. I would do massive water changes to bring down the high ammonia reading. And/or add a good ammonia remover like “De-Tox Plus” ASAP.   
 

For good   Koifish care : You want a high enough reading of KH in your  koi fish pond to maintain your pH level of above 7 overnight. If your pH is dropping below 7 you must add a buffer like our  “Buff-it-Up” which contains life supporting carbonates to give your pH a good foundation of KH. A good solid foundation of carbonates will keep your  koi fish and your  life supporting "good bacteria" healthy.