Alkaline Ph

[mark4785]

Hi,

I have been keeping fish in a 1400 litre pond for about 18 months. It has 4 Koi, 3 goldfish, 1 shubunkin, 1 green tench, 3 golden orfe, 1 golden rudd and 2 ghost carp. My ammonia, nitrite and nitrate levels have remained at a solid zero. My water GH is only 4 which prompted me to put a medication mixture in to increase it to the recommended level. The water KH is 7.

However, my PH level is going excessively alkaline with the recent water test showing it to be between 8.4 and 8.8. I have tried to remedy the problem by applying 'Pond PH down' product by Ntlabs but multiple doses of this have done nothing; I think the PH may have even increased during the time I was applying this product!

I want to maintain a healthy PH level of 8.0 and was wondering if somebody could provide tips on what other things I can do to achieve this.

Note: My pond has a well growing carex pendula plant with a height of about 25cm. I thought I'd mention this as I know plants can change the water chemistry.

Thanks,

Mark.

 

[mark4785]

The water PH is now 8.8. I am now trying to lower this reading with a product named 'Nt Labs PH and KH buffer'. The KH level is currently 6 so hopefully the remedy will buffer it to a more recommended level and also deal with the PH problem.

My other water parameters are perfect but the alkalinity of the water as seemingly caused a koi to jump out of the water and hit the side of the filter box according to my Dad. I really do need to lower the PH of the water, but I am in a tricky situation as my tap water has a PH of 7.5 so removing 50% of the pond water in order to bring the PH down will cause the PH to drop too much. A recent chemistry article I read stated an artificial change of the PH should not exceed 0.2 units in a 24 hour period.

Does anybody have any advice that I could follow?

Note: The fish will not have jumped out due to a parasitic issue or wound. There are no wounds on any of the fish and all equipment/plants and fish are disinfected before they are added to the pond.

 

[mark4785]

I think I know what is causing the high alkalinity. There appears to be some blanket weed growing all around the base of the pond which is a form of phytoplankton which apparently absorbs c02 or carbonic acid/dioxide in the water during daylight hours and during night time. The effect is that my pond has no c02 within it which is causing alkalosis, and would fully explain why the Koi tried to leap out of the pond.

I am thinking of doing 50/60% water change as my tap water is 7.5 (this will reduce the overall PH) and keep dosing the pond with aligicides.