Hello
I’m new to the forum and I appreciate your advice .
We’re located in Sinai, Egypt and unfortunately, no koi enthusiasts around..
we have 3 large natural ponds and one small hydroponics koi pond . All use RO water , oldest pond has 20 years , never had any problems with water quality or fish ( occasionally we lost fish to predator birds or cats over the years ) .
Hydroponics pond , 2 years old, 850 liters, around 50 young koi and butterflies there at the moment (10-20cm, 1 to 2 years old ) . It works as an inverted fountain with plant buckets all around and water falling back to pond creating waterfalls , daily we add 5-10% water due to evaporation and plants, in summer twice a day . Recently we moved 15 butterflies out to bigger natural pond, they were growing much faster than others ..
afterwards, About 2 weeks ago , 1 koi died at night , in morning pond was smelly , ammonia .25 , nitrate 1
Changed 50% water , ammonia back to 0, but nitrate 0.5
Since than we’ve changed 30 % water every few days ( besides daily adding water ), but nitrate always at best 0.5
We use API kit , 7.6 ph ( always, all ponds ) , nitrite 0 , high range ph 7.4-8
I’m wondering what is causing the high nitrate ?
What am I missing/ forgetting ?
Is it the fish growing and pooping more or water quality issue ( same water has perfect readings in other ponds ) .
Thank you
Lucy