I have had my koi pond (3000 gals ) for 13 years and I now have 7 large koi 16"-22". All appear to be very healthy. I have a bead filter and 1/3 HP pump which pumps 3300 gph and also I use 2- 40 watt UV lighting. The water stays very clear. I also use Micro-lift koi clay and Aqua-Medzyme DC every 2 weeks . This has worked very well for me as I have not had any issues with their health. Now my problem is halfway through last year and all of this year my water tests have been terrible. PH 6.0 Ammonia 8.0 Nitrite 0 Phosphate (off the chart ) Nitrate 20.0 KH ( off the chart ). I have done water changes of 3-4 hundred gal but that does not seem to help. I also have 300 bio-balls and course matting at my water fall outlet. My koi are feed 1/3 solol cup of food every day and every other day and evening small treat. My question is what am I doing wrong? These fish have been with me since they were yearlings and as you know we get very attached to them. This site has been very informative for me over the years but I really need some good advice. Thanks Note : I am not using the tub of beneficial bacteria as shown but am asking , should I possibly try this ???