Complacency

I always considered myself an experienced fish keeper and today I have come down to earth with a bang.
My filtration system has been running successfully for two years - parameters were spot on and with only minute fluctuations - so much so that I have been routinely testing the water parameters assuming that everything would be ok - very little food going in periodic top ups after cleaning the nexus. Decided today (thank god) to do a spring clean of my ponds and get a base reading on the parameters ready for the oncoming season.
To my horror (and a severe case of my clacker valve doing half a crown sixpence half a crown sixpence) pH was 4.5 (sera test)!! mind in overdrive "fish are ok swimming around happily" "not over feeding" "nothing appears untoward" must be a dodgy test - retest - the same- retest with Kusuri 5 ! retest with API 6 - digital pH on the pond showing 5.21. Tested KH - 0 !! Tested the growing pond pH and everything ok - all readings between 7 and 7.5
No idea why the main pond's pH was crashing but I done a complete overhaul and will have to do small water changes over the next week to bring up the pH gradually. Lesson learnt !! that was one close call

Dont feel too bad about it Richard your complacency is shared by many people who have done exactly the same thing and been caught out by their own experience.

I dont claim to know the science of why it happens but it does. With 2 systems running from the same source water one must take into consideration the indoor setup still has an active bio system, where as the outdoor pond will have non without any heat.The main learning curve with this is that you wont do it again and that you do know how to deal with it.

main pond back up to 6.5 and kh 2 - fish appear totally unbothered by all this

Thats good to hear, so which test kit was giving the correct reading ?

strangely enough none including the digitals - i recalibrated them today and they are ok now but used the remainder of the calibration fluid to test the test kits
Calibration fluid 7.1
Sera read - 6
kusuri 6.5
API 6
REALLY GOT TO TRY TO MAINTAIN A DECENT KH

It has been the bane of my koi keeping hobby, maintaining a kH & pH reading suitable for koi. Here is a picture of the best method to date I have found. Stacks of Lithaqua well 100kg to be precise, it works well and since installing it I have not had a problem with pH crashes. Many people have copied this setup.

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where do you have this installed chrissy?

Lol they are stacked across the end of my bio chamber after the jap matting 3 stacks of 10 trays fit wall to wall, with air stones underneath so the water passes through and makes contact with the lithaqua.

not an option for me because I am filtered by Nexus

I made these a couple of years ago when the pond was built and did the job at the time. With the new Koi Masters Advantage/ Replenish available hopefully these will not be needed anymore.

my thoughts too