[saratogatan]

My pond that is. pond 6200g, filter 1400g. changed water 15%+, twice a week.

The story: more than a month ago, I noticed that all koi in my pond with beni started to show sign of receeding/thining beni, except 2 beni koi who are not affected. For example, the inazuma kohaku that won best in size in the April NorCal show is now a 4 step kohaku. The beni on another kohaku that used to be very thick was thinned to the point that it was light orange.

The things different this year from last:
- new koi food in late may. I used Ogata staple this year, plus hikari sinking wheatgerm. I used hikari wheatgerm last year.
- started light Ogata Silk power in mid Jun.
- koi spawned in early may, 6 spwaned. Last year, 1 spawned in Mid Jul.

On all of those koi, the trace of prior beni can still be identify, the tone of the 'new shiro' (more like light orange) is different.

I have stopped the ogata food all together for 2 weeks. started Hi-silk sweet potato+silkworm. The one kohaku with massive beni thinning is recovering that I can call those beni. The rest are yet to recover.

Question : What could be the cuase of my problem ? Is there any chance the beni maybe recovered ? Any specific food I need to feed the koi to stop the problem ?

I am way over-stocked. There are about 600" of koi in my pond, average 250 gallon of water per koi.

All suggestions are highly appreciated.

stan