Hi,

I have 3 established, connected ponds where for the first time (in 8 years!) we are losing fish - approximately 3 a day, mostly in 2 of the ponds but occasionally in the 3rd. While I believe this is due to the high temperatures and not enough aeration, I wanted to see if anyone has any advice for me. I had lost my pond thermometer and just got another one today, and all 3 ponds are running about 85 degrees during and after the heat of the day. I'll check temp again in the morning to see where we're at. We are located in NC, zone 7a, and temps are running about 98 (in the shade) during the day and 70 at night.

Pond details:

Pond #1 - top pond
approx 2000 gallons, max depth 3.5 to 4 feet, water is pumped up from pond #3 (bottom pond) into small waterfall basin. Bottom drain has aerator attached. This pond has 8 koi, all in for about a month, about 4 inches in size. Shubunkin (also about 4 inches) have all died from this pond in the last week.

This pond is in shade until about 1 pm, then gets direct sun for about 3-4 hours. I only have about 15% coverage from water lilies, and have been adding additional shade via a patio umbrella. No koi losses so far (crossing fingers.) Pic below.

Pond #2 - middle pond

also approx 2000 gallons, water moves over slight waterfall into this pond from pond #1. More shallow than pond #1, max depth of about 3.5 to 4 feet. Pond only has shubunkin, most small (2 inches or so.) I have lost almost all of the bigger shubunkin out of this pond over the last week or so (4-5 inches) and some smaller ones. Pond also has bottom drain. This pond is shaded until about 2:00, then gets full sun for about 2 hours. Bottom drain has aerator. Water is also pumped up from bottom pond via diverter that is usually underwater, just today I've raised the pipe above waterlevel to provide additional waterfall/splash.

Pond #3 - bottom pond

Approx 6500 gallons, pretty consistent depth of 4 - 4.5 feet. Mix of koi and shubunkin. We lost a lot of fish over the winter (we are away for the winter with just aerators left on so no idea where they all went - suspect predators or snakes in the spring). Water comes down from 2 waterfall system from middle pond through short "creek" to this pond. Full sun. Bottom drain, also aerated, pumps through two barrel filtration system and is pumped to other side of bottom pond through bog filter (bog also has bottom drain) and back over small waterfall into pond. This pump has slowed down from last year and we are not getting as fast of a rush over this waterfall. Losing mostly the larger (4-5 inch) shubunkin and also some smaller shubunkin and mixes.

My fish load is pretty small this year to start out with. I am emptying the bottom drains morning and night. The ponds are getting a 20 minute fill about 5 pm every day from cold well water. I suspect this is a problem with lack of oxygen, as the fish are dying overnight. Outside of ordering more aerators, does anyone else have any thoughts on this? It's been this hot before, for this long, and I didn't have any fish deaths like this in years past. PH is between 7.5 and 8. Ponds are clear, though algae is growing fast right now.

Does anyone have any ideas or think I'm on the wrong track?

Thanks,

--Samantha
Boiling Springs, NC