Thread: Ph risen after fluke solve plus - coincidence?

Originally Posted by stevo8003

Can I just ask if anyone using fluke solve plus has found it affects ph please as mine’s climbed to 9.0. I am currently doing a water change but with 100,000 litres that could take a while - so should I add some ph adjuster perhaps? Dont like adjusting ph too rapidly but 9.0 seems dangerously high to me. PS Fluke solve has been in 7 days now

I've never used Fluke Solve Plus so I can't comment on that part of your post but, although pH 9 is high, it isn't dangerously high so you could allow it to fall naturally due to biological activity in the biofilter and water changes rather than try to get it to its more usual value by adding an acidic compound.

I could be more specific if you gave the normal pH and KH values and the values of your supply (after it has been dechlorinated and aerated for a few hours).

Ok, you're on the way to getting the pH back to its usual value just by water changes and one water change has dropped the pH by 0.4 which leaves 0.8 to go but you can't just add or subtract pH values because it's a logarithmic scale.

I could explain the pH logarithmic scale if anyone wants a headache but the simplest example relevant to this situation is that a pH of 8.8 is ten times more alkaline than pH 7.8 so, if you want to drop the pH by 0.8 (from 8.6 to 7.8), two more water changes of the same volume won't do it. However, two more changes should drop the pH to just above 8.0 at which point you could ignore the difference and allow it to fall just by biological action alone.

Yep, you're on the correct track but do you know why the pH varies from morning to night? If not, this may help:

Photosynthesis removes dissolved CO₂ so many people blame it for causing pH variations but the correct way to look at photosynthesis is to consider that it doesn't cause the variations, it restores your pH to its normal value after CO₂ from fish respiration has lowered it during the night. That may seem odd but this explanation might make pH variations easier to understand:

Measure your pH at the end of a sunny day when photosynthesis has removed as much of the dissolved CO₂ as possible and call that your natural pond pH. Measure it again as early as possible in the morning and the difference between the two is caused by dissolved CO₂ due to fish respiration.

If there were no fish in the pond, there would be no downward night time pH change caused by the increase in dissolved CO₂ for photosynthesis to restore or, if you suddenly added a load of fish without altering the aeration, the night time reduction in pH due to the increase in dissolved CO₂ would be greater. So, photosynthesis should be seen as helping to restore the natural pH by removing the variable parameter (dissolved CO₂) that lowers pH rather than photosynthesis causing an upward variation.

Koi can happily adjust to any pH in the range 7.0 to 8.5 but they have to make biological changes to keep their blood pH in a narrow range (7.7 to 8.0) regardless of the pond pH and the maximum pH variation they can cope with without becoming stressed is 0.2 per day. If you want to reduce the daily variation, first try greatly increasing aeration to gas off the excess CO₂ and, if that doesn't reduce it enough, you will have to increase the KH with a possible increase in pH.