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Thread: GH and KH dilemma
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23-09-2018, 02:49 PM #1
GH and KH dilemma
I've kept koi for around 10 years. I live in Yorkshire where the water is 'soft'. I read years ago that this was best for koi. Now I am hovering towards harder water as I've read it has more minerals in it which is beneficial for koi's bones. I can see logic in that, we need calcium for our bones too, and salt.
I have never experienced a PH crash, my PH stayed around 6.5 slightly acidic but I was happy with that as it was a buffer for other low/high readings incl. temp. I admit I never tested for GH or KH on a regular basis, just testing PH, ammonia, nitrite and nitrate. But after getting spikes I think due to putting in new sponges and over zealous with filter cleaning I decided to test everything with a fresh test kit. I was alarmed to see my KH was only 2 Dh and my GH was only 4 Dh (Pondlab says on the test kit ) it should be 6 and 8. So I ordered buffers from NT labs which I added. 7 weeks on, and several part water changes the KH is still 2 but GH has gone up slighlty to 5. I just buffered again proportionately. But then I tested the tap water and guess what, KH is 2 Dh and GH is 6 Dh. Now my fish (all types) are used to this and I feel constant buffering is going to upset what they are used to and cost money in the process. So what do I do? Keep buffering every two water changes or, if the fish seem happy just keep an eye on the PH and give them certain foods, to compensate in their diet. oh, and since buffering my PH is more alkaline now 7-8.
The old adage - 'if it ain't broke don't fix it' or is that just tempting fate??
Last edited by hopeful; 23-09-2018 at 04:29 PM.
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23-09-2018, 03:07 PM #2
I'm not a believer in koi needing to swim in a mineral soup to get the minerals they need. They can get all that in their food. Even in winter if you are not really feeding the weed and algae they chomp on are a plentiful supply of nutrients. My koi don't have any issues with swimming around in zero GH water (RO).
The KH is obviously a very different issue- you need some or your filter bacteria can't function, and to prevent pH crashes. But it is surprising how little is needed for this. I keep my KH at around 15 ppm (just below 1DH). Some people have found they need to go a bit higher than that to keep nitrite at bay though.
When I first started running RO I was worried I would get large pH swings- after all carbonates are buffers. However in my pond the opposite has been true. pH is remarkably stable for a full-sun pond, and fluctuates between 7.1 and 7.3 at the most. Before with my hard water I was getting large pH swings of 8.1 to 8.6, which the koi really did not like.
You've very lucky to have soft water- I would save a heap of cash if I had what you do2016 new 6000 gallon pond
https://www.koiforum.uk/pond-construc...ghlight=feline
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23-09-2018, 04:34 PM #3
Thank you Feline, that is such a relief. I will buffer the KH then, that will help with the nitrite issue hopefully, I will leave the GH alone, but I will keep checking it of course.
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